Most downloaded articles
2021, 50(9):3116-3124.
DOI: 10.12442/j.issn.1002-185X.20200548
Abstract:
CoCrFeNi high entropy alloys (HEAs) were prepared by electro-deoxidization of metal oxides in CaCl2 molten salt at 1173 K. The phase transformation from the metal oxides to HEA under different electrolysis durations was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The results show that the formation process of CoCrFeNi HEA includes two stages: the rapid deoxidization stage and deep deoxidization stage. In the rapid deoxidization stage, 93.93wt% oxygen in sintered oxide pellet is removed within 1 h and the current efficiency reaches 89.95%. After electrolysis of 15 h, the oxygen content of the product is 0.26wt% and the current efficiency is 17.93%. The formation process of CoCrFeNi HEA provides guidance for establishing the electrochemical route with low cost and high efficiency.
CoCrFeNi high entropy alloys (HEAs) were prepared by electro-deoxidization of metal oxides in CaCl2 molten salt at 1173 K. The phase transformation from the metal oxides to HEA under different electrolysis durations was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The results show that the formation process of CoCrFeNi HEA includes two stages: the rapid deoxidization stage and deep deoxidization stage. In the rapid deoxidization stage, 93.93wt% oxygen in sintered oxide pellet is removed within 1 h and the current efficiency reaches 89.95%. After electrolysis of 15 h, the oxygen content of the product is 0.26wt% and the current efficiency is 17.93%. The formation process of CoCrFeNi HEA provides guidance for establishing the electrochemical route with low cost and high efficiency.
2009, 38(2):368-372.
Abstract:
Noble metal core-shell nanoparticles have attracted much attention due to their unique optical, electric and catalytic properties, they can be applied in material sciences, biophysics, molecular electronics and fluorescence-spectral engineering based on surface- enhancement. In this paper, a comprehensive review is presented on noble metal core-shell nanoparticles including preparation, application, and then the development trends of noble metal core-shell materials were also proposed
Noble metal core-shell nanoparticles have attracted much attention due to their unique optical, electric and catalytic properties, they can be applied in material sciences, biophysics, molecular electronics and fluorescence-spectral engineering based on surface- enhancement. In this paper, a comprehensive review is presented on noble metal core-shell nanoparticles including preparation, application, and then the development trends of noble metal core-shell materials were also proposed
2009, 38(3):443-446.
Abstract:
The flexible ITO films were fabricated on PET substrate by Ion Beam Assisted Deposition(IBAD), and the effects of SiO2 buffer layer on the properties of ITO films were researched. The properties of ITO films were studied using X-ray diffraction (XRD), UV-VIS spectrometer, four-point probe and optical profiler. The results show that the SiO2 interlayer between ITO films and PET results in an increase of X-ray peak intensity of ITO film and a decrease of resistivity to 1.21×10-3 Ω·cm; in addition, the transmittance decreases to 85% and the surface is relatively smooth. The resistivity of the ITO films bent to some extent keeps some stability
The flexible ITO films were fabricated on PET substrate by Ion Beam Assisted Deposition(IBAD), and the effects of SiO2 buffer layer on the properties of ITO films were researched. The properties of ITO films were studied using X-ray diffraction (XRD), UV-VIS spectrometer, four-point probe and optical profiler. The results show that the SiO2 interlayer between ITO films and PET results in an increase of X-ray peak intensity of ITO film and a decrease of resistivity to 1.21×10-3 Ω·cm; in addition, the transmittance decreases to 85% and the surface is relatively smooth. The resistivity of the ITO films bent to some extent keeps some stability
2009, 38(3):477-480.
Abstract:
The content and distributing of P in Electroless Nickel/Immersion Gold (ENIG) surface finishes effect the reliability of interface between solder joint and surface finishes. 289 I/Os lead-free Sn-3.0Ag-0.5Cu BGAs was assembled on the ENIG print circuit board by reflow soldering technology. The print circuit board was tested by random vibration. After random vibration test, the failure and not failure samples were studied by X-ray, SEM, and EDX et al. The failure mechanism was confirmed and the relation of failure and content and distributing of P in ENIG finishes was discussed. The failure and not failure samples after vibration test show similar microstructure at the interface of solder joint and surface finishes. The cross-sectioning of the affected area shows a “tooth decay” effect of corrosion of the nickel layer, and “mud cracks” in the topography on the surface. The enrichment of P on the surface accelerated the oxidation of Ni, and also reduced the mechanical intensity of interface. The oxidation of Ni and the enrichment of P on the surface result in the crack of solder/finish interface
The content and distributing of P in Electroless Nickel/Immersion Gold (ENIG) surface finishes effect the reliability of interface between solder joint and surface finishes. 289 I/Os lead-free Sn-3.0Ag-0.5Cu BGAs was assembled on the ENIG print circuit board by reflow soldering technology. The print circuit board was tested by random vibration. After random vibration test, the failure and not failure samples were studied by X-ray, SEM, and EDX et al. The failure mechanism was confirmed and the relation of failure and content and distributing of P in ENIG finishes was discussed. The failure and not failure samples after vibration test show similar microstructure at the interface of solder joint and surface finishes. The cross-sectioning of the affected area shows a “tooth decay” effect of corrosion of the nickel layer, and “mud cracks” in the topography on the surface. The enrichment of P on the surface accelerated the oxidation of Ni, and also reduced the mechanical intensity of interface. The oxidation of Ni and the enrichment of P on the surface result in the crack of solder/finish interface
2009, 38(2):373-376.
Abstract:
Introduce the application area of rhenium including petrochemical, aeronautics and astronautics, metallurgy and electron industry and others. Systemic summarize and analyzed the main preparation methods of rhenium products, point out various preparation methods of rhenium and rhenium alloys
Introduce the application area of rhenium including petrochemical, aeronautics and astronautics, metallurgy and electron industry and others. Systemic summarize and analyzed the main preparation methods of rhenium products, point out various preparation methods of rhenium and rhenium alloys
2010, 39(2):367-371.
Abstract:
Al2O3/ZrO2 coating was deposited on γ-TiAl based alloys with aluminum isopropoxide (Al(OC3H7)3) and zirconium oxychloride octahydrate (ZrOCl2?8H2O) as starting materials by sol-gel method. The coating synthesized using dip-coating process, was uniform and crack-free. Isothermal and cyclic oxidations of the coated and uncoated specimens at 1000 ℃ in static air were carried out to test the coating effect on the oxidation behavior of the alloy. The coating decreases the oxidation rate of the alloys and increases the cyclic oxidation resistance. The possible mechanism of the coating on the oxidation behavior of the alloy was discussed
Al2O3/ZrO2 coating was deposited on γ-TiAl based alloys with aluminum isopropoxide (Al(OC3H7)3) and zirconium oxychloride octahydrate (ZrOCl2?8H2O) as starting materials by sol-gel method. The coating synthesized using dip-coating process, was uniform and crack-free. Isothermal and cyclic oxidations of the coated and uncoated specimens at 1000 ℃ in static air were carried out to test the coating effect on the oxidation behavior of the alloy. The coating decreases the oxidation rate of the alloys and increases the cyclic oxidation resistance. The possible mechanism of the coating on the oxidation behavior of the alloy was discussed
2009, 38(2):259-262.
Abstract:
The microstructure of Ti-6Al-4V joints by laser beam welding with different welding parameters was studied, and the tensile properties were investigated. The microstructure of welding seam by laser beam welding consists mainly of α′ martensite phase as well as some α″ phase. By increasing the weld heat input，the distribution of martensite becomes more dispersive and glomerate due to the molten pool stiring, the welding stress and the burning loss of alloy elements. However, the welding parameters have no obviously effects on both the phase composition and the phase ratio. The tensile strength of joints is higher than basal metal when welded with reasonable parameters
The microstructure of Ti-6Al-4V joints by laser beam welding with different welding parameters was studied, and the tensile properties were investigated. The microstructure of welding seam by laser beam welding consists mainly of α′ martensite phase as well as some α″ phase. By increasing the weld heat input，the distribution of martensite becomes more dispersive and glomerate due to the molten pool stiring, the welding stress and the burning loss of alloy elements. However, the welding parameters have no obviously effects on both the phase composition and the phase ratio. The tensile strength of joints is higher than basal metal when welded with reasonable parameters
2009, 38(3):515-518.
Abstract:
Au colloid was prepared by reducing HAuCl4·4H2O with Na3C6H5O7·2H2O. The effects of reductant amounts, mixing procedures, reaction time and stirring speed on the concentration, size, shape and monodispersity of Au colloid were investigated. UV-vis and TEM were used to characterize the size, shape, structure and optical properties of the samples. It's found that the optimal conditions for preparing Au colloid of small size are Na3C6H5O7(aq):HAuCl4(aq)=3:1(V:V), mixing Na3C6H5O7 firstly, reacting for 6 min and 650 r/min stirring speed. The colloid was prepared successfully which has superiority in shape, monodispersity and stability. The size of nanoparticles is only about 6~7 nm
Au colloid was prepared by reducing HAuCl4·4H2O with Na3C6H5O7·2H2O. The effects of reductant amounts, mixing procedures, reaction time and stirring speed on the concentration, size, shape and monodispersity of Au colloid were investigated. UV-vis and TEM were used to characterize the size, shape, structure and optical properties of the samples. It's found that the optimal conditions for preparing Au colloid of small size are Na3C6H5O7(aq):HAuCl4(aq)=3:1(V:V), mixing Na3C6H5O7 firstly, reacting for 6 min and 650 r/min stirring speed. The colloid was prepared successfully which has superiority in shape, monodispersity and stability. The size of nanoparticles is only about 6~7 nm
2009, 38(3):398-403.
Abstract:
The complexity and diversity of microstructural information involved in Ti alloys makes it rather difficult to quantitatively analyze properties or describe microstructural evolution behavior. Feasible and rigorous models capable of quantifying various microstructural data are rarely researched. Based on metallographical characteristics and mechanism of microstructure evolution, applying the stereology and quantitative Metallography rules, a preliminary system of models and methods for quantifying many important microstructural features of Ti alloys was developed. The work is an exploration for investigating the microstructure evolution and the relationship between microstructure and performance of Ti alloys. These microstructural features mainly include phase volume fraction, β grain size, thickness of Widmanst?tten α laths, colony size, and α phase information (size/orientation/aspect) in some microstructures. Six rules for manual-splitting α phase on image processing was presented. These models and methods are feasible, and explained with some examples
The complexity and diversity of microstructural information involved in Ti alloys makes it rather difficult to quantitatively analyze properties or describe microstructural evolution behavior. Feasible and rigorous models capable of quantifying various microstructural data are rarely researched. Based on metallographical characteristics and mechanism of microstructure evolution, applying the stereology and quantitative Metallography rules, a preliminary system of models and methods for quantifying many important microstructural features of Ti alloys was developed. The work is an exploration for investigating the microstructure evolution and the relationship between microstructure and performance of Ti alloys. These microstructural features mainly include phase volume fraction, β grain size, thickness of Widmanst?tten α laths, colony size, and α phase information (size/orientation/aspect) in some microstructures. Six rules for manual-splitting α phase on image processing was presented. These models and methods are feasible, and explained with some examples
2010, 39(1):182-188.
Abstract:
Recent research progress of inorganic sulfides electrode materials for lithium-ion batteries，including binary metal sulfides, oxysulfides, Chevrel phase compounds, thiospinels and thio-phosphates, is summarized. The prospect of the electrode materials in future is previewed. Thio-phosphates and other polyanion sulfides are considered as promising electrode materials.
Recent research progress of inorganic sulfides electrode materials for lithium-ion batteries，including binary metal sulfides, oxysulfides, Chevrel phase compounds, thiospinels and thio-phosphates, is summarized. The prospect of the electrode materials in future is previewed. Thio-phosphates and other polyanion sulfides are considered as promising electrode materials.
2009, 38(8):1333-1337.
Abstract:
The microstructures of as-SHSed Stellite 6 and as-cast HS111 were investigated by SEM, XRD and EPMA. It was shown that there is significant similarity in the microstructures of as-SHSed Stellite 6 and as-cast HS111. But carbides of continuous cast HS111 alloy can form single and uniform carbides phase.
The microstructures of as-SHSed Stellite 6 and as-cast HS111 were investigated by SEM, XRD and EPMA. It was shown that there is significant similarity in the microstructures of as-SHSed Stellite 6 and as-cast HS111. But carbides of continuous cast HS111 alloy can form single and uniform carbides phase.
2009, 38(3):384-388.
Abstract:
A layer of TiO2 film was prepared by sol-gel method on the surface of TLM(Ti-3Zr-2Sn-3Mo-25Nb) alloy. Then the coated samples were treated by hydroxyl solution and amination solution in order to introduce the OH- and NH2- active groups, and the heparin was linked on the surface of TiO2 film through these active groups. The phase identification and the surface characteristics of the samples were successively undertaken using XRD, SEM and EDS. The in vitro blood compatibility of the TLM alloy specimens with and without heparinization treatments was evaluated by the contact angle test, the hemolysis test and investigation of their platelet adhesion behavior. The results showed that the haemocompatibility of the TLM alloy could be significantly improved by surface modification via heparinization.
A layer of TiO2 film was prepared by sol-gel method on the surface of TLM(Ti-3Zr-2Sn-3Mo-25Nb) alloy. Then the coated samples were treated by hydroxyl solution and amination solution in order to introduce the OH- and NH2- active groups, and the heparin was linked on the surface of TiO2 film through these active groups. The phase identification and the surface characteristics of the samples were successively undertaken using XRD, SEM and EDS. The in vitro blood compatibility of the TLM alloy specimens with and without heparinization treatments was evaluated by the contact angle test, the hemolysis test and investigation of their platelet adhesion behavior. The results showed that the haemocompatibility of the TLM alloy could be significantly improved by surface modification via heparinization.
2009, 38(11):1997-2000.
Abstract:
The microstructures of both as-cast and heat treated Mg-2.54Nd-0.26Zn-0.32Zr alloy were investigated by means of XRD, DTA, OM and TEM in this study. The results show that the massive Mg-RE phase Mg12Nd is mainly distributed on the grain boundary of as-cast Mg-2.54Nd-0.26Zn-0.32Zr. Only a small amount of flaky and grainy Mg12Nd distribute in the intracrystalline and grain boundary. The Mg12Nd phase is uniformly distributed on the matrix as crossed plate gathered by spotted state phase after solution and aging treatment.
The microstructures of both as-cast and heat treated Mg-2.54Nd-0.26Zn-0.32Zr alloy were investigated by means of XRD, DTA, OM and TEM in this study. The results show that the massive Mg-RE phase Mg12Nd is mainly distributed on the grain boundary of as-cast Mg-2.54Nd-0.26Zn-0.32Zr. Only a small amount of flaky and grainy Mg12Nd distribute in the intracrystalline and grain boundary. The Mg12Nd phase is uniformly distributed on the matrix as crossed plate gathered by spotted state phase after solution and aging treatment.
2009, 38(12):2136-2140.
Abstract:
Hot workability of metal molybdenum was investigated by means of hot compression tests carried out in the temperature range of 900~1450 ℃ and strain rate range of 0.01~10 s-1. A constitutive equation of molybdenum for the flow stress was presented. The radial precision forging process of the molybdenum bar was simulated by COGGING modular of FEM software DEFORM. Reasonable process parameters were determined, and the forging penetration efficiency was explored from the strain-effective state. The results show that the forging penetration efficiency criterion put forward for the simulation result analysis is reasonable. Determination methods of the process and parameters are correct. Research shows that the main factors influencing forging penetration efficiency are reduction in pass and the dip angle of the hammer, and the main factors influencing forged piece surface quality are axle feeding speed and rotation angle.
Hot workability of metal molybdenum was investigated by means of hot compression tests carried out in the temperature range of 900~1450 ℃ and strain rate range of 0.01~10 s-1. A constitutive equation of molybdenum for the flow stress was presented. The radial precision forging process of the molybdenum bar was simulated by COGGING modular of FEM software DEFORM. Reasonable process parameters were determined, and the forging penetration efficiency was explored from the strain-effective state. The results show that the forging penetration efficiency criterion put forward for the simulation result analysis is reasonable. Determination methods of the process and parameters are correct. Research shows that the main factors influencing forging penetration efficiency are reduction in pass and the dip angle of the hammer, and the main factors influencing forged piece surface quality are axle feeding speed and rotation angle.
2009, 38(3):496-499.
Abstract:
A new technology for preparation of TaC coating on Carbon/carbon composites is reported. TaC was turned from TaO2F·rH2O·TaF5, which was characterized by FITR, XRD and SEM. The morphologies of TaC coating at different temperatures were observed by SEM. At 1200 ℃, the TaC coating shows the particular form. When the heat treatment temperature increased to 1800 ℃, the TaC coating was mainly columnar. The formation mechanism of TaC is that Carbon atom diffuse into Ta2O5 deposit, which is coming from TaO2F·rH2O·TaF5 and reacted into TaC at high temperature. The morphology of TaC coating can be interpreted by the theory of Ta2O5 deposited nucleation
A new technology for preparation of TaC coating on Carbon/carbon composites is reported. TaC was turned from TaO2F·rH2O·TaF5, which was characterized by FITR, XRD and SEM. The morphologies of TaC coating at different temperatures were observed by SEM. At 1200 ℃, the TaC coating shows the particular form. When the heat treatment temperature increased to 1800 ℃, the TaC coating was mainly columnar. The formation mechanism of TaC is that Carbon atom diffuse into Ta2O5 deposit, which is coming from TaO2F·rH2O·TaF5 and reacted into TaC at high temperature. The morphology of TaC coating can be interpreted by the theory of Ta2O5 deposited nucleation
16 Corrosion Processing Dissolution Characteristics of Ti-6Al-4V in Hydrofluoric –Nitric Acid System
2016, 45(10):2628-2634.
Abstract:
The effects of main solution ingredients, temperature on dissolution and characteristics of corrosion processing for Ti-6Al-4V in hydrofluoric-nitric acid system were investigated by means of E-t curve, potentiodynamic polarization curve. Moreover anodic and cathodic reaction rate measurements were used to discuss corrosion dynamics. The process of “attack→oxidation→dissolution” repeats continuously during the course of corrosion dissolution of titanium alloy in this solution system. The growth and destruction of passive film simultaneously occur. Corrosion processing rate tends to be stable when the growth of passive film and dissolution of the substrate achieve dynamic balance. At the early stage of corrosion processing, corrosion potential changes to a more positive value when the concentration of hydrofluoric acid is low, indicating that oxide film is difficult to be attacked, while in case of higher concentration, corrosion potential becomes negative quickly as oxide film is easily dissolved. Corrosion dissolution rate is affected by hydrofluoric acid concentration and temperature. With the increase of hydrofluoric acid concentration and temperature, the activation energy declines, corrosion dissolution is enhanced. Temperature plays a leading role under the condition of lower concentration of hydrofluoric acid. When the concentration reaches 80mL/L, the influence of temperature attenuates and the concentration of hydrofluoric acid becomes the major factor.
The effects of main solution ingredients, temperature on dissolution and characteristics of corrosion processing for Ti-6Al-4V in hydrofluoric-nitric acid system were investigated by means of E-t curve, potentiodynamic polarization curve. Moreover anodic and cathodic reaction rate measurements were used to discuss corrosion dynamics. The process of “attack→oxidation→dissolution” repeats continuously during the course of corrosion dissolution of titanium alloy in this solution system. The growth and destruction of passive film simultaneously occur. Corrosion processing rate tends to be stable when the growth of passive film and dissolution of the substrate achieve dynamic balance. At the early stage of corrosion processing, corrosion potential changes to a more positive value when the concentration of hydrofluoric acid is low, indicating that oxide film is difficult to be attacked, while in case of higher concentration, corrosion potential becomes negative quickly as oxide film is easily dissolved. Corrosion dissolution rate is affected by hydrofluoric acid concentration and temperature. With the increase of hydrofluoric acid concentration and temperature, the activation energy declines, corrosion dissolution is enhanced. Temperature plays a leading role under the condition of lower concentration of hydrofluoric acid. When the concentration reaches 80mL/L, the influence of temperature attenuates and the concentration of hydrofluoric acid becomes the major factor.
Deng Zhenbo
,
zhouchangchun
,
Fan Yujiang
,
Peng Jingping
,
Zhu Xiangdong
,
Pei Xuan
,
Yin Guofu
,
Zhang Xingdong
2016, 45(9):2287-2292.
Abstract:
In order to fabricate bone tissue engineering scaffold accurately, a novel method that combines parametric modeling and 3D printing was proposed. In this method, the scaffold structures were designed using cloud data of molded surface. Firstly, the cloud data containing the surface information of Cube structure, Diamond structure and Gryriod structure were obtained. Then the scaffold structures with different parameters were expressed by mathematical functions. After that, finite element analysis was done to the scaffolds. The mechanical properties of porous scaffolds were calculated based on finite element analysis. Bone tissue engineering scaffolds with differentSporous structures were manufactured by 3D printing. Finally, characterizations of printed titanium scaffolds were done to detect the porosity and mechanical properties. The results show that the parameterized model and rapid prototyping manufacturing can design and fabricate titanium alloy scaffolds with specific pore structure characteristics effectively. And the scaffold"s mechanical properties can be also designed. It realized porous titanium alloy scaffolds with optimized biological functions from the perspective of bionics.
In order to fabricate bone tissue engineering scaffold accurately, a novel method that combines parametric modeling and 3D printing was proposed. In this method, the scaffold structures were designed using cloud data of molded surface. Firstly, the cloud data containing the surface information of Cube structure, Diamond structure and Gryriod structure were obtained. Then the scaffold structures with different parameters were expressed by mathematical functions. After that, finite element analysis was done to the scaffolds. The mechanical properties of porous scaffolds were calculated based on finite element analysis. Bone tissue engineering scaffolds with differentSporous structures were manufactured by 3D printing. Finally, characterizations of printed titanium scaffolds were done to detect the porosity and mechanical properties. The results show that the parameterized model and rapid prototyping manufacturing can design and fabricate titanium alloy scaffolds with specific pore structure characteristics effectively. And the scaffold"s mechanical properties can be also designed. It realized porous titanium alloy scaffolds with optimized biological functions from the perspective of bionics.
2016, 45(8):1924-1930.
Abstract:
In aluminum alloy droplet deposition manufacture，thermal warping，layering and hot cracking of formed 3D components are the most common defects, which have been found to be associated with the larger temperature gradient and thermal stress concentraction. To obtain insight into the common defects formation mechanism in metal micro-droplet deposition manufacture, a 3D transient finite element (FE) simulation model has been developed by using the APDL(ANSYS) code and element brith-death technique. The distribution and variation of time-dependent temperature and thermal stress fields were predicted and the thermo-mechanical behaviors were analyzed in fabricating aluminum alloy 3D components. And then, a series of deposition experiments were conducted using 7075Al alloy droplets under the setting process parameters(Same to the simulation initial and boundary conditions). The experimental results show that the experimental results basically agree with the simulation results of thermo-mechanical behaviors. The reliability and correctness of the simulation model were verified experimentally by the measured temperature field and the observation of thermal deformation and hot cracking of formed 3D component. The work provides an useful theoretical and experimental guide for optimizing metal droplets deposition manufacture.
In aluminum alloy droplet deposition manufacture，thermal warping，layering and hot cracking of formed 3D components are the most common defects, which have been found to be associated with the larger temperature gradient and thermal stress concentraction. To obtain insight into the common defects formation mechanism in metal micro-droplet deposition manufacture, a 3D transient finite element (FE) simulation model has been developed by using the APDL(ANSYS) code and element brith-death technique. The distribution and variation of time-dependent temperature and thermal stress fields were predicted and the thermo-mechanical behaviors were analyzed in fabricating aluminum alloy 3D components. And then, a series of deposition experiments were conducted using 7075Al alloy droplets under the setting process parameters(Same to the simulation initial and boundary conditions). The experimental results show that the experimental results basically agree with the simulation results of thermo-mechanical behaviors. The reliability and correctness of the simulation model were verified experimentally by the measured temperature field and the observation of thermal deformation and hot cracking of formed 3D component. The work provides an useful theoretical and experimental guide for optimizing metal droplets deposition manufacture.
2009, 38(6):955-957.
Abstract:
The deformed microstructures and mechanical properties of commercial pure titanium (CP-Ti) with an initial grain size of about 28 μm was investigated using equal channel angular pressing (ECAP). ECAP was conducted at room temperature adopting a die with a channel angle of 120° via route BC. Special attention was paid on the microstructure evolution and mechanical properties of the ECAP samples. Deformation twins were found in most grains after the first and second pass of ECAP. After four ECAP passes, the original grains were refined from 28 μm to about 250 nm, and the ultimate strength and microhardness were significantly enhanced to 773 MPa and 2486 MPa, respectively. Meanwhile good ductility of 16.8% elongation still remained.
The deformed microstructures and mechanical properties of commercial pure titanium (CP-Ti) with an initial grain size of about 28 μm was investigated using equal channel angular pressing (ECAP). ECAP was conducted at room temperature adopting a die with a channel angle of 120° via route BC. Special attention was paid on the microstructure evolution and mechanical properties of the ECAP samples. Deformation twins were found in most grains after the first and second pass of ECAP. After four ECAP passes, the original grains were refined from 28 μm to about 250 nm, and the ultimate strength and microhardness were significantly enhanced to 773 MPa and 2486 MPa, respectively. Meanwhile good ductility of 16.8% elongation still remained.
2009, 38(2):327-330.
Abstract:
Using sodium hypophosphite as the reducing agent, polyvinyl pyrrolidone as the protecting agent, the nanosized silver powder was synthesized by chemical reduction method in a highly concentrated silver nitrate solution. Using the orthogonal design method of three factors and three levels, the optimal conditions to prepare the nanosized silver powder were obtained by studying the effects of following factors, such as the concentration of reducing agent, the doses of protecting agent and the temperature, on the particles size and morphology of silver powder. The pure nanosized silver powders with qusai-spherical shapes and homogeneous distribution and diameter of 30 nm to 50 nm were synthesized under the conditions of AgNO3 concentration of 1.0 mol/L, NaH2PO2·H2O concentration of 0.1 mol/L, PVP/AgNO3 weight ratio of 1∶1, pH=1~2 and at 40 ℃
Using sodium hypophosphite as the reducing agent, polyvinyl pyrrolidone as the protecting agent, the nanosized silver powder was synthesized by chemical reduction method in a highly concentrated silver nitrate solution. Using the orthogonal design method of three factors and three levels, the optimal conditions to prepare the nanosized silver powder were obtained by studying the effects of following factors, such as the concentration of reducing agent, the doses of protecting agent and the temperature, on the particles size and morphology of silver powder. The pure nanosized silver powders with qusai-spherical shapes and homogeneous distribution and diameter of 30 nm to 50 nm were synthesized under the conditions of AgNO3 concentration of 1.0 mol/L, NaH2PO2·H2O concentration of 0.1 mol/L, PVP/AgNO3 weight ratio of 1∶1, pH=1~2 and at 40 ℃
2009, 38(9):1613-1617.
Abstract:
The strengthening effects of Al-Zr-Cr-La dispersoids to Al-Mg alloys have investigated. The results show that adding Cr and La and adding Zr, Cr and La at tha same time can improve the hardness and strength and the capability to inhibit the recrystalization for the Al-Mg alloys. Comparing wih adding Cr and La, adding Zr, Cr and La at the same time has more obvious effect to inhibit the recrystalization and increase their hardness and strength
The strengthening effects of Al-Zr-Cr-La dispersoids to Al-Mg alloys have investigated. The results show that adding Cr and La and adding Zr, Cr and La at tha same time can improve the hardness and strength and the capability to inhibit the recrystalization for the Al-Mg alloys. Comparing wih adding Cr and La, adding Zr, Cr and La at the same time has more obvious effect to inhibit the recrystalization and increase their hardness and strength
22 Study on the preparation of dense spherical molybdenum powders with high purity via induction plasma
2016, 45(5):1325-1329.
Abstract:
Using induction plasma, spheroidization, densification, refinement and purity of molybdenum powder were realized, Dense spherical powders with high purity were prepared. The effects of the plasma power and particle size of raw molybdenum powder on spheroidization efficiency of products were studied. The phase composition，morphologies and particle size distributions of the powder before and after spheroidization were characterized by x-ray diffraction(XRD),scanning electron microscopy(SEM) and laser micron sizer(LMS).The result show that the spherical molybdenum powder can be obtained from irregular powder after induction plasma spheroidization. The powder presents smooth surface and good disparity, and the spheroidization efficiency is almost 100%.After plasma treatment, the particle size become finer and its distribution is more concentrated. Under otherwise identical conditions, ,spheroidization efficiency increases firstly and then decreases with the increasing of plasma power. When the plasma power is 25kW,the effects of spheroidization is best. Smaller the particle size, higher the spheroidization efficiency is. With the increasing of spheriodization efficiency, the powder flow ability and apparent density have been significantly improved. The molybdenum powder flow ability is improved from 40s／50g to 11s／50g, and the apparent density from 2.3g／cm3 to 6.1g／cm3.
Using induction plasma, spheroidization, densification, refinement and purity of molybdenum powder were realized, Dense spherical powders with high purity were prepared. The effects of the plasma power and particle size of raw molybdenum powder on spheroidization efficiency of products were studied. The phase composition，morphologies and particle size distributions of the powder before and after spheroidization were characterized by x-ray diffraction(XRD),scanning electron microscopy(SEM) and laser micron sizer(LMS).The result show that the spherical molybdenum powder can be obtained from irregular powder after induction plasma spheroidization. The powder presents smooth surface and good disparity, and the spheroidization efficiency is almost 100%.After plasma treatment, the particle size become finer and its distribution is more concentrated. Under otherwise identical conditions, ,spheroidization efficiency increases firstly and then decreases with the increasing of plasma power. When the plasma power is 25kW,the effects of spheroidization is best. Smaller the particle size, higher the spheroidization efficiency is. With the increasing of spheriodization efficiency, the powder flow ability and apparent density have been significantly improved. The molybdenum powder flow ability is improved from 40s／50g to 11s／50g, and the apparent density from 2.3g／cm3 to 6.1g／cm3.
Li Jianfeng
,
Zhang Pingxiang
,
Liu Xianghong
,
Li Jinshan
,
Feng Yong
,
Wang Tiancheng
,
Du Shejun
,
Liu Weitao
,
G. Grunblatt
,
C. Verwaerde
,
G. K. Hoang
2009, 38(2):263-265.
Abstract:
This paper shows the results of R&D program carried out to optimize NbTi wires for the Poloidal Field (PF) coils of ITER. The influence of heat treatment on the microstructure was investigated by using TEM to find the relations between the microstructure and the critical current densities at 4.2 K for NbTi superconducting composite wire. Typical microstructure (in transverse cross-section) shows α-Ti pinning centers dispersed within the superconducting β-NbTi matrix with strong fold and curl for the NbTi wire with high critical current density at 4.2 K. It is believed that the higher temperature is beneficial to a higher Jc value at 4.2 K, but the Jc values slightly decrease with increasing the heat treatment times
This paper shows the results of R&D program carried out to optimize NbTi wires for the Poloidal Field (PF) coils of ITER. The influence of heat treatment on the microstructure was investigated by using TEM to find the relations between the microstructure and the critical current densities at 4.2 K for NbTi superconducting composite wire. Typical microstructure (in transverse cross-section) shows α-Ti pinning centers dispersed within the superconducting β-NbTi matrix with strong fold and curl for the NbTi wire with high critical current density at 4.2 K. It is believed that the higher temperature is beneficial to a higher Jc value at 4.2 K, but the Jc values slightly decrease with increasing the heat treatment times
2009, 38(3):456-459.
Abstract:
The electrochemical reduction process of Zr(Ⅳ) was studied at molybdenum electrodes in K2ZrF6-LiCl-KCl molten salt at 923 K by transient electrochemical techniques, such as cyclic voltammetry, chronopotentiometry and chronoamperometry. The experimental results show that Zr(Ⅳ) was reduced to Zr metal by a two-step mechanism corresponding to the Zr(Ⅳ)/Zr(Ⅱ) and Zr(Ⅱ)/Zr transition. The intermediate product was identified as ZrCl2 by X-ray diffraction. The chronoamperometric studies indicate that nucleation polarization existed during the electrodeposition process of zirconium at molybdenum electrode. This polarization is an instantaneous nucleation process
The electrochemical reduction process of Zr(Ⅳ) was studied at molybdenum electrodes in K2ZrF6-LiCl-KCl molten salt at 923 K by transient electrochemical techniques, such as cyclic voltammetry, chronopotentiometry and chronoamperometry. The experimental results show that Zr(Ⅳ) was reduced to Zr metal by a two-step mechanism corresponding to the Zr(Ⅳ)/Zr(Ⅱ) and Zr(Ⅱ)/Zr transition. The intermediate product was identified as ZrCl2 by X-ray diffraction. The chronoamperometric studies indicate that nucleation polarization existed during the electrodeposition process of zirconium at molybdenum electrode. This polarization is an instantaneous nucleation process
2009, 38(4):565-569.
Abstract:
Single-crystalline GaN nanowires have been synthesized on Si(111) substrates by magnetron sputtering through ammoniating the Ga2O3/Nb films at 900 °C in a quartz tube. The as-prepared nanowires are confirmed as single crystalline GaN with wurtzite structure by X-ray diffraction (XRD), selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). Transmission electron microscopy (TEM) shows that the GaN nanowires are straight and smooth, and possess the diameters of about 50 nm and lengths up to several microns. When excited by 325 nm helium-cadmium (He-Cd) laser light at room temperature, the GaN nanowires only have a strong ultraviolet luminescence peak located at 367 nm, owing to GaN band-edge emission. Finally, the growth mechanism of GaN nanowires is discussed briefly.
Single-crystalline GaN nanowires have been synthesized on Si(111) substrates by magnetron sputtering through ammoniating the Ga2O3/Nb films at 900 °C in a quartz tube. The as-prepared nanowires are confirmed as single crystalline GaN with wurtzite structure by X-ray diffraction (XRD), selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). Transmission electron microscopy (TEM) shows that the GaN nanowires are straight and smooth, and possess the diameters of about 50 nm and lengths up to several microns. When excited by 325 nm helium-cadmium (He-Cd) laser light at room temperature, the GaN nanowires only have a strong ultraviolet luminescence peak located at 367 nm, owing to GaN band-edge emission. Finally, the growth mechanism of GaN nanowires is discussed briefly.
2009, 38(2):255-258.
Abstract:
Microstructure and formation characteristic of laser welded lap joints of TC4 alloy were investigated, and a parameter named join rate ψ was introduced to evaluate the welding effect of lap welding. The results indicated: the width of weld bead increases with increasing laser power or decreasing welding velocity, the top width of weld bead is larger than the bottom width and the minimum is the middle layer. And the join rate decreases as plates space or energy input increases. Microstructure of weld bead consisted of α′ martensite, and the martensite in the top portion is more concentrate than that in the bottom portion. There ate a small amount of martensite in HAZ, and distributed in gradient. For the strengthen effect of martensite, the microhardness reduces from the center of joints to base metal in cross direction, and the microhardness is higher in top weld bead
Microstructure and formation characteristic of laser welded lap joints of TC4 alloy were investigated, and a parameter named join rate ψ was introduced to evaluate the welding effect of lap welding. The results indicated: the width of weld bead increases with increasing laser power or decreasing welding velocity, the top width of weld bead is larger than the bottom width and the minimum is the middle layer. And the join rate decreases as plates space or energy input increases. Microstructure of weld bead consisted of α′ martensite, and the martensite in the top portion is more concentrate than that in the bottom portion. There ate a small amount of martensite in HAZ, and distributed in gradient. For the strengthen effect of martensite, the microhardness reduces from the center of joints to base metal in cross direction, and the microhardness is higher in top weld bead
2009, 38(3):559-564.
Abstract:
In this paper, the fabrication methods of magnesium matrix composites were introduced and the new fabrication process was emphasized. The effects of the fabrication processes on the composition, structure and properties of the composites were analyzed. Developing new reinforcements and novel in-situ reaction synthesis, optimizing the fabrication process and preparing high performance composites on larger scale are main research keys to the magnesium matrix composites
In this paper, the fabrication methods of magnesium matrix composites were introduced and the new fabrication process was emphasized. The effects of the fabrication processes on the composition, structure and properties of the composites were analyzed. Developing new reinforcements and novel in-situ reaction synthesis, optimizing the fabrication process and preparing high performance composites on larger scale are main research keys to the magnesium matrix composites
2009, 38(3):532-535.
Abstract:
Using simple and efficient template method, sphere assembled structure; shuttle-like structure and flake assembled structure of calcium carbonate were obtained. The morphologies of products were researched, and the sphere assembled calcium carbonate with large surface was modified and combined with silver nanoparticles to obtain the silver nanoparticle/calcium carbonate composite for the first time. The composite has extensive applications in sterilization and medicine areas etc. The composite can not only reduce the silver quantity, but also provide a good route for applications of calcium carbonate nanomaterials
Using simple and efficient template method, sphere assembled structure; shuttle-like structure and flake assembled structure of calcium carbonate were obtained. The morphologies of products were researched, and the sphere assembled calcium carbonate with large surface was modified and combined with silver nanoparticles to obtain the silver nanoparticle/calcium carbonate composite for the first time. The composite has extensive applications in sterilization and medicine areas etc. The composite can not only reduce the silver quantity, but also provide a good route for applications of calcium carbonate nanomaterials
2015, 44(1):255-260.
Abstract:
At present, the lithium-ion battery is mainly limited by safety, high-power performance and cost. These problems are expected to be solved by new high-performance anode material of lithium titanate oxides. Based on the recent research progress, several representative lithium-titanium-oxygen species lithium intercalation compounds such as Li4Ti5O12, LiTi2O4, Li2Ti3O7, and Li2Ti6O13 are selected. The important achievements of their crystal structures, electrochemical properties, preparation methods, chemical modifications and application researches are comprehensively elaborated. Finally, the direction of future research and development for such anode materials are pointed out.
At present, the lithium-ion battery is mainly limited by safety, high-power performance and cost. These problems are expected to be solved by new high-performance anode material of lithium titanate oxides. Based on the recent research progress, several representative lithium-titanium-oxygen species lithium intercalation compounds such as Li4Ti5O12, LiTi2O4, Li2Ti3O7, and Li2Ti6O13 are selected. The important achievements of their crystal structures, electrochemical properties, preparation methods, chemical modifications and application researches are comprehensively elaborated. Finally, the direction of future research and development for such anode materials are pointed out.
2009, 38(9):1505-1508.
Abstract:
A novel type of foundry method for TiAl-based alloy is presented in the present paper. The filling processes of Ti-47Al alloy sheet and blade have been studied via numerical simulation. The investigation results indicate that the filling fraction is enhanced by the increase of filling velocity and graphite throat diameter. The graphite throat diameter is the main parameter for the backward filling location in the process of vacuum suction casting. With the increase of mould temperature, the solid fraction is reduced. The alloy solidification begins from bottom to top. The TiAl sheet and the blade are produced by this method. The grain size of the sheet is in the range from 10 μm to 40 μm. There is no obvious shrinkage cavity
A novel type of foundry method for TiAl-based alloy is presented in the present paper. The filling processes of Ti-47Al alloy sheet and blade have been studied via numerical simulation. The investigation results indicate that the filling fraction is enhanced by the increase of filling velocity and graphite throat diameter. The graphite throat diameter is the main parameter for the backward filling location in the process of vacuum suction casting. With the increase of mould temperature, the solid fraction is reduced. The alloy solidification begins from bottom to top. The TiAl sheet and the blade are produced by this method. The grain size of the sheet is in the range from 10 μm to 40 μm. There is no obvious shrinkage cavity
2016, 45(9):2444-2448.
Abstract:
In this paper, graphene oxide was prepared as raw material by the improved Hummers method. Then graphene-Fe3O4 magnetic carrier was obtained by co-precipitation method, finally TiO2/graphene-Fe3O4 magnetic ternary complex photocatalyst was synthesized by hydrothermal method. The properties of products were characterized by XRD, SEM, and UV-Vis DRS. Photocatalytic activity and stability of the resulting catalyst was evaluated by the degradation of methylene blue solution under visible and UV light. It was found that the degradation reaction accorded with first-order kinetic model. The composite catalyst had better photocatalytic activity than pure TiO2 in the UV and visible light. As a support and electron acceptor, graphene extended and enhanced the band edge absorption of TiO2 into the visible light region, so it could effectively enhance the photocatalytic activity of TiO2. At the same time magnetic Fe3O4 was added to improve its recyclability.
In this paper, graphene oxide was prepared as raw material by the improved Hummers method. Then graphene-Fe3O4 magnetic carrier was obtained by co-precipitation method, finally TiO2/graphene-Fe3O4 magnetic ternary complex photocatalyst was synthesized by hydrothermal method. The properties of products were characterized by XRD, SEM, and UV-Vis DRS. Photocatalytic activity and stability of the resulting catalyst was evaluated by the degradation of methylene blue solution under visible and UV light. It was found that the degradation reaction accorded with first-order kinetic model. The composite catalyst had better photocatalytic activity than pure TiO2 in the UV and visible light. As a support and electron acceptor, graphene extended and enhanced the band edge absorption of TiO2 into the visible light region, so it could effectively enhance the photocatalytic activity of TiO2. At the same time magnetic Fe3O4 was added to improve its recyclability.
2009, 38(2):219-223.
Abstract:
An isothermal and constant strain rate compression test is carried out for the Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy with an equiaxed α+β microstructure in the temperature range of 1020~1080 ℃ and the strain rate range of 0.001~70 s-1. A power dissipation map is developed on the basis of flow stress data and by using the principles of dynamic material model. The results show that the steady state flow characteristics exist during hot compression deformation for the Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy in the temperature range 1020~1080 ℃. The dynamic recrystallization regime was identified in the power dissipation map and the microstructure examination was performed for validation. In the β phase field, the dynamic recrystallization occured in the temperature range of 1020~1080 ℃ and the strain rate range of 0.01~0.1 s-1 with the efficiency of power dissipation η mostly larger than 0.4, which is the optimum β forging processing parameters. It is proved that the power dissipation map based on dynamic material model is an effective method for successful β-forging and microstructure control
An isothermal and constant strain rate compression test is carried out for the Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy with an equiaxed α+β microstructure in the temperature range of 1020~1080 ℃ and the strain rate range of 0.001~70 s-1. A power dissipation map is developed on the basis of flow stress data and by using the principles of dynamic material model. The results show that the steady state flow characteristics exist during hot compression deformation for the Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy in the temperature range 1020~1080 ℃. The dynamic recrystallization regime was identified in the power dissipation map and the microstructure examination was performed for validation. In the β phase field, the dynamic recrystallization occured in the temperature range of 1020~1080 ℃ and the strain rate range of 0.01~0.1 s-1 with the efficiency of power dissipation η mostly larger than 0.4, which is the optimum β forging processing parameters. It is proved that the power dissipation map based on dynamic material model is an effective method for successful β-forging and microstructure control
2010, 39(1):80-84.
Abstract:
The rare earth element yttrium was added into 7055 aluminum alloys in the form of Al-Y intermediate alloy. The thermodynamic mechanism during melting and effect mechanism during solidification of yttrium were analyzed based on the classical theories of physical chemistry and crystal growth. Results show that there are strong binding between yttrium and impurity elements, such as oxygen, hydrogen, nitrogen, sulfur, iron and so on, which can purify the aluminum melt. The grain size of as-cast alloys is decreased from 60-70 μm to 40-50 μm after yttrium addition. It is due to the small solubility of yttrium element in molten aluminum. Most of yttrium segregates at the solid-liquid boundary, and prevent the Zn, Mg and Cu atoms from diffusing resulting in the constitutional supercooling at the frontier of solidification, which accelerate the growth of cellular dendrite. Furthermore, the amount of eutectic increases, the size of which is smaller than that without yttrium.
The rare earth element yttrium was added into 7055 aluminum alloys in the form of Al-Y intermediate alloy. The thermodynamic mechanism during melting and effect mechanism during solidification of yttrium were analyzed based on the classical theories of physical chemistry and crystal growth. Results show that there are strong binding between yttrium and impurity elements, such as oxygen, hydrogen, nitrogen, sulfur, iron and so on, which can purify the aluminum melt. The grain size of as-cast alloys is decreased from 60-70 μm to 40-50 μm after yttrium addition. It is due to the small solubility of yttrium element in molten aluminum. Most of yttrium segregates at the solid-liquid boundary, and prevent the Zn, Mg and Cu atoms from diffusing resulting in the constitutional supercooling at the frontier of solidification, which accelerate the growth of cellular dendrite. Furthermore, the amount of eutectic increases, the size of which is smaller than that without yttrium.
2010, 39(1):85-89.
Abstract:
spicule and flake with big sizes on the surface of the milling-free powders, while on the surface of milled powders ZnO was shaped mainly as spicule with small sizes. Nodules of virtually pure silver atoms formed on the surface of powder during internal oxidation, which is attributed to the compressive stress caused by the expansion of ZnO in the silver-matrix during internal oxidation.
spicule and flake with big sizes on the surface of the milling-free powders, while on the surface of milled powders ZnO was shaped mainly as spicule with small sizes. Nodules of virtually pure silver atoms formed on the surface of powder during internal oxidation, which is attributed to the compressive stress caused by the expansion of ZnO in the silver-matrix during internal oxidation.
2009, 38(4):691-695.
Abstract:
The V2O5 thin film was prepared on the substrates of Si glass and commercial glass by the sol-gel technique. The samples prepared were annealed in air atmosphere at different temperatures. The microstructure, the morphology and optical properties of V2O5 thin films were studied by XRD, SEM and spectrophotometer. The results of XRD and SEM indicate that the better crystalline states and orientation with V2O5 (001) and (200) after annealing can be obtained, and the grain homogeneity on nano-V2O5 film surface can be improved through proper increasing of annealing temperatures; The results of transmission and absorption spectra show that a red shift will occur at the absorption edges of V2O5 films, and optical band gaps are shortened gradually with the increase of annealing temperature.
The V2O5 thin film was prepared on the substrates of Si glass and commercial glass by the sol-gel technique. The samples prepared were annealed in air atmosphere at different temperatures. The microstructure, the morphology and optical properties of V2O5 thin films were studied by XRD, SEM and spectrophotometer. The results of XRD and SEM indicate that the better crystalline states and orientation with V2O5 (001) and (200) after annealing can be obtained, and the grain homogeneity on nano-V2O5 film surface can be improved through proper increasing of annealing temperatures; The results of transmission and absorption spectra show that a red shift will occur at the absorption edges of V2O5 films, and optical band gaps are shortened gradually with the increase of annealing temperature.
2009, 38(3):468-472.
Abstract:
In this paper, soldered lap joint specimens were fabricated by a solder reflow process using a Sn-3.8Ag-0.7Cu-xRE (x=0, 0.1wt%, 0.25wt%, 0.5wt%) BGA solder ball on FR4 substrate parts. The effects of rare earth(RE) content and strain rate on the shear properties of soldered lap joint were investigated. The Results show that the addition of minute RE (<0.25wt%) can improve the shear strength and elongation of the lap joint. However, further increasing of RE content would degrade the shear properties of the lap joint. The shear strength and elongation of the lap joint increase with the increase of strain rate. The analysis of the microstructure and fractograph indicated that through the addition of minute RE, the microstructure of the lap joint was refined, especially the growth of intermetallic compound was inhibited, and thus the shear properties of the lap joint were improved. In addition, the observation of fractographs confirmed that the elongation of the lap joint increase with the increase of strain rate
In this paper, soldered lap joint specimens were fabricated by a solder reflow process using a Sn-3.8Ag-0.7Cu-xRE (x=0, 0.1wt%, 0.25wt%, 0.5wt%) BGA solder ball on FR4 substrate parts. The effects of rare earth(RE) content and strain rate on the shear properties of soldered lap joint were investigated. The Results show that the addition of minute RE (<0.25wt%) can improve the shear strength and elongation of the lap joint. However, further increasing of RE content would degrade the shear properties of the lap joint. The shear strength and elongation of the lap joint increase with the increase of strain rate. The analysis of the microstructure and fractograph indicated that through the addition of minute RE, the microstructure of the lap joint was refined, especially the growth of intermetallic compound was inhibited, and thus the shear properties of the lap joint were improved. In addition, the observation of fractographs confirmed that the elongation of the lap joint increase with the increase of strain rate
2009, 38(3):426-430.
Abstract:
Transverse mechanical properties of TMCs reinforced by two types of SiC fibers with and without C coating were determined by use of cross-shaped specimens. The initial nonlinear stress of the stress-strain curve under the applied transverse tensile load was adopted to calculate the interface strength. The interface strength with C coating was 53 MPa which was lower than 196 MPa of the one without C coating. The debonding position of two interface were different, i.e. the former was between the fiber and C coating, but the latter was between the matrix and reaction products. The initial nonlinearity stress of TMCs reinforced by multiple fibers with 30% volume fraction was lower than that of single fiber reinforced TMCs, which was caused by the decrease of residual stress on the surface of fiber, and the interface strength was not influenced by the more additional fibers
Transverse mechanical properties of TMCs reinforced by two types of SiC fibers with and without C coating were determined by use of cross-shaped specimens. The initial nonlinear stress of the stress-strain curve under the applied transverse tensile load was adopted to calculate the interface strength. The interface strength with C coating was 53 MPa which was lower than 196 MPa of the one without C coating. The debonding position of two interface were different, i.e. the former was between the fiber and C coating, but the latter was between the matrix and reaction products. The initial nonlinearity stress of TMCs reinforced by multiple fibers with 30% volume fraction was lower than that of single fiber reinforced TMCs, which was caused by the decrease of residual stress on the surface of fiber, and the interface strength was not influenced by the more additional fibers
2020, 49(5):1576-1582.
DOI: 10.12442/j.issn.1002-185X.E20190003
Abstract:
In this study, porous Zn-xMg alloy scaffolds (x=5,10 and 15 wt.%) were fabricated as bone tissue engineering scaffold by spark plasma sintering (SPS) using same volume content space holder (NaCl). The effect of content of Mg on the mechanical properties, microstructural characterizations of the porous Zn-xMg alloys scaffold were revealed. Results showed that with increasing content of Mg, the porosity increased from 40.3% to 54.3% and the mean open pore size increased from 289 μm to 384 μm due to the dealloying effect of Mg. Mechanical tests results showed that porous Zn-Mg alloy was a typical elastic-brittle metallic foam and porous Zn-10Mg was best among three scaffolds. The strength and elastic module of the scaffolds showed good biomechanical compatibility and had the promising to be used as a lower load-bearing implant material.
In this study, porous Zn-xMg alloy scaffolds (x=5,10 and 15 wt.%) were fabricated as bone tissue engineering scaffold by spark plasma sintering (SPS) using same volume content space holder (NaCl). The effect of content of Mg on the mechanical properties, microstructural characterizations of the porous Zn-xMg alloys scaffold were revealed. Results showed that with increasing content of Mg, the porosity increased from 40.3% to 54.3% and the mean open pore size increased from 289 μm to 384 μm due to the dealloying effect of Mg. Mechanical tests results showed that porous Zn-Mg alloy was a typical elastic-brittle metallic foam and porous Zn-10Mg was best among three scaffolds. The strength and elastic module of the scaffolds showed good biomechanical compatibility and had the promising to be used as a lower load-bearing implant material.
2009, 38(2):224-228.
Abstract:
In this article the strain controlled and stress controlled low cycle fatigue behaviors of TC21 titanium alloy were investigated. The fatigue tests were performed at room temperature and cyclic strain and stress ratio of 0.1 with triangle load wave. During the initial stage of strain controlled fatigue, the cyclic tensile stresses soften rapidly and the cyclic compressive stresses harden rapidly at the same time, the rates of cyclic softening and cyclic hardening decrease with the fatigue progress. During the overall fatigue progress, the soften rate is related to the cyclic strain but little to the cyclic stress, which is related to the macro friction stresses. Obvious cyclic creep occurs under the stress controlled low cycle fatigue conditions, and the magnitude of cyclic creep strain is related to the maximum cyclic stress. The softening of tensile friction stresses is the main factor of cyclic creep.
In this article the strain controlled and stress controlled low cycle fatigue behaviors of TC21 titanium alloy were investigated. The fatigue tests were performed at room temperature and cyclic strain and stress ratio of 0.1 with triangle load wave. During the initial stage of strain controlled fatigue, the cyclic tensile stresses soften rapidly and the cyclic compressive stresses harden rapidly at the same time, the rates of cyclic softening and cyclic hardening decrease with the fatigue progress. During the overall fatigue progress, the soften rate is related to the cyclic strain but little to the cyclic stress, which is related to the macro friction stresses. Obvious cyclic creep occurs under the stress controlled low cycle fatigue conditions, and the magnitude of cyclic creep strain is related to the maximum cyclic stress. The softening of tensile friction stresses is the main factor of cyclic creep.
2016, 45(9):2269-2274.
Abstract:
Magnesium alloys have a significant advantage-low density over other structure metals currently and have been widely used in various fields such as transportation and aerospace. With the development of further research and the enlargement of research scope, more advantages have been developed: high storage capacity, high theoretical volumetric energy density, extraordinarily high damping capacity, good biocompatibility, excellent shielding efficiency as well as impressive thermal conductivity. Therefore Mg alloys have the potential to be various functional materials, such as hydrogen storage material, rechargeable electrochemical batteries, damping material, biodegradable implant material, electromagnetic shielding material, and thermal conductive material. Unfortunately, each kind of functional material has bottlenecks or troubles needing to be broken through, and a lot of researches have been carried out in recent years. This review comprehensively covers the research history, progress and the up-to-date summary of Mg and Mg alloys as functional materials. The six kinds of materials above all will be discussed respectively.
Magnesium alloys have a significant advantage-low density over other structure metals currently and have been widely used in various fields such as transportation and aerospace. With the development of further research and the enlargement of research scope, more advantages have been developed: high storage capacity, high theoretical volumetric energy density, extraordinarily high damping capacity, good biocompatibility, excellent shielding efficiency as well as impressive thermal conductivity. Therefore Mg alloys have the potential to be various functional materials, such as hydrogen storage material, rechargeable electrochemical batteries, damping material, biodegradable implant material, electromagnetic shielding material, and thermal conductive material. Unfortunately, each kind of functional material has bottlenecks or troubles needing to be broken through, and a lot of researches have been carried out in recent years. This review comprehensively covers the research history, progress and the up-to-date summary of Mg and Mg alloys as functional materials. The six kinds of materials above all will be discussed respectively.
Yang Zhaozhu
,
Xue Chengshan
,
Zhuang Huizhao
,
Wang Gongtang
,
Chen Jinhua
,
Li Hong
,
Qin Lixia
,
Wang Zouping
2009, 38(3):377-379.
Abstract:
Large-scale GaN nanowires were synthesized on Si(111) substrates through ammoniating Ga2O3/V films. The as-grown products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results reveal that the grown GaN nanowires have a smooth and clean surface with diameters ranging from 20 nm to 60 nm and lengths of about several tens of micrometers. The results of HRTEM and selected-area electron diffraction (SAED) show that the nanowires are pure hexagonal GaN single crystal. The photoluminescence (PL) spectrum indicates that the GaN nanowires have good emission property. The growth mechanism is discussed briefly.
Large-scale GaN nanowires were synthesized on Si(111) substrates through ammoniating Ga2O3/V films. The as-grown products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results reveal that the grown GaN nanowires have a smooth and clean surface with diameters ranging from 20 nm to 60 nm and lengths of about several tens of micrometers. The results of HRTEM and selected-area electron diffraction (SAED) show that the nanowires are pure hexagonal GaN single crystal. The photoluminescence (PL) spectrum indicates that the GaN nanowires have good emission property. The growth mechanism is discussed briefly.
42 Preparation and Cytocompatibility of Bioactive β-TCP Coatings on Porous Magnesium Scaffold Surface
2009, 38(2):318-322.
Abstract:
A chemical deposition route was employed to prepare bioactive β-TCP coatings on porous magnesium scaffold surfaces. The phase identification and surface morphology of the specimens were studied by X-ray diffraction and scanning electron microscope, respectively. The cytocompatibility of treated porous magnesium scaffolds was studied in the present paper by using human osteoblast-like UMR106 cells. It was found that the cytotoxicity was in grade 1, indicating cytotoxicity free and without damage to DNA and no change to the cell cycle for the extracted liquid of treated magnesium. All the experimental results indicate that the treated porous magnesium has a good cytocompatibility and potential to be a new type of bone tissue engineering scaffolds
A chemical deposition route was employed to prepare bioactive β-TCP coatings on porous magnesium scaffold surfaces. The phase identification and surface morphology of the specimens were studied by X-ray diffraction and scanning electron microscope, respectively. The cytocompatibility of treated porous magnesium scaffolds was studied in the present paper by using human osteoblast-like UMR106 cells. It was found that the cytotoxicity was in grade 1, indicating cytotoxicity free and without damage to DNA and no change to the cell cycle for the extracted liquid of treated magnesium. All the experimental results indicate that the treated porous magnesium has a good cytocompatibility and potential to be a new type of bone tissue engineering scaffolds
2015, 44(9):2234-2239.
Abstract:
The morphology and growth behavior of interfacial intermetallic compound (IMC) layer for the Sn3.0Ag0.5Cu0.05Cr (SACCr)/Cu joints after isothermal aging at 150 °C for 0, 168, 500 and 1000 h were investigated, and they were compared with Sn3.0Ag0.5Cu (SAC). The results show that the trace Cr dispersed or dissolved in SAC solder effectively inhibits the IMC layer growth at the interface of SACCr/Cu joints. The longer the aging time, the more obvious the inhibiting effect of Cr on the overgrowth of IMC layer of solder/Cu joints. The average thickness of IMC layer of SACCr/Cu solder joints is about 5.13 μm after aging for 1000 h, only 45% of that of the SAC/Cu solder joints.
The morphology and growth behavior of interfacial intermetallic compound (IMC) layer for the Sn3.0Ag0.5Cu0.05Cr (SACCr)/Cu joints after isothermal aging at 150 °C for 0, 168, 500 and 1000 h were investigated, and they were compared with Sn3.0Ag0.5Cu (SAC). The results show that the trace Cr dispersed or dissolved in SAC solder effectively inhibits the IMC layer growth at the interface of SACCr/Cu joints. The longer the aging time, the more obvious the inhibiting effect of Cr on the overgrowth of IMC layer of solder/Cu joints. The average thickness of IMC layer of SACCr/Cu solder joints is about 5.13 μm after aging for 1000 h, only 45% of that of the SAC/Cu solder joints.
2010, 39(2):352-356.
Abstract:
The microstructure and mechanical properties of Al-Mg2Si alloys by equal channel angular pressing (ECAP) at 250 oC were studied. Vickers hardness and tensile testing show that the hardness, tensile strength and elongation of the alloys increase after ECAP for 4 passes. However, the hardness and tensile strength decrease after ECAP for 8 passes while the elongation increases further. SEM and TEM observations show that the original skelecton shape or the Chinese-script Mg2Si phase are obviously broken after ECAP. The more the extrusion passes, the more the fragmentated Mg2Si phase, and the more the alloys refining. The mechanism for the decrease in hardness and tensile strength of the specimen after ECAP for 8 passes compared with 4 passes was discussed.
The microstructure and mechanical properties of Al-Mg2Si alloys by equal channel angular pressing (ECAP) at 250 oC were studied. Vickers hardness and tensile testing show that the hardness, tensile strength and elongation of the alloys increase after ECAP for 4 passes. However, the hardness and tensile strength decrease after ECAP for 8 passes while the elongation increases further. SEM and TEM observations show that the original skelecton shape or the Chinese-script Mg2Si phase are obviously broken after ECAP. The more the extrusion passes, the more the fragmentated Mg2Si phase, and the more the alloys refining. The mechanism for the decrease in hardness and tensile strength of the specimen after ECAP for 8 passes compared with 4 passes was discussed.
2009, 38(3):554-558.
Abstract:
TiAl-based alloys are emerging as potential light-weight, high-temperature structural materials and possess wide capacities of engineering applications in aeronautics, space and automobile industries because of their low density, high specific strength and specific modulus, good oxidation-resistance and creep-resistance, and excellent fatigue properties. The paper will focus on the melting and investment casting technology of TiAl-based alloys. Some applications of TiAl components are summarized and some shortcomings and challenges for the investment casting of TiAl-based alloys are also proposed
TiAl-based alloys are emerging as potential light-weight, high-temperature structural materials and possess wide capacities of engineering applications in aeronautics, space and automobile industries because of their low density, high specific strength and specific modulus, good oxidation-resistance and creep-resistance, and excellent fatigue properties. The paper will focus on the melting and investment casting technology of TiAl-based alloys. Some applications of TiAl components are summarized and some shortcomings and challenges for the investment casting of TiAl-based alloys are also proposed
2009, 38(3):519-522.
Abstract:
The effect of the frequency of the pulsed magnetic field on Mg-Gd-Y-Zr alloy during solidification was investigated. When the pulsed magnetic field is applied to Mg-Gd-Y-Zr alloy during the solidification process, the grain refinement is achieved. The average grain size of the as-cast Mg-Gd-Y-Zr alloy is from 65 mm without the pulsed magnetic filed to 37 mm with the pulsed magnetic field of 5 Hz. Grain refinement of Mg-Gd-Y-Zr alloy is due to the electromagnetic undercooling and reduction of temperature gradient by the vibration of melt resulted from the pulsed magnetic field. Compared those casting method with traditional one, the tensile strength and elongation are increased by 4.8% and 78.5%, respectively
The effect of the frequency of the pulsed magnetic field on Mg-Gd-Y-Zr alloy during solidification was investigated. When the pulsed magnetic field is applied to Mg-Gd-Y-Zr alloy during the solidification process, the grain refinement is achieved. The average grain size of the as-cast Mg-Gd-Y-Zr alloy is from 65 mm without the pulsed magnetic filed to 37 mm with the pulsed magnetic field of 5 Hz. Grain refinement of Mg-Gd-Y-Zr alloy is due to the electromagnetic undercooling and reduction of temperature gradient by the vibration of melt resulted from the pulsed magnetic field. Compared those casting method with traditional one, the tensile strength and elongation are increased by 4.8% and 78.5%, respectively
2009, 38(3):527-531.
Abstract:
The preparation and formability of 30W-Cu EFP(explosively formed projectile) liner were studied. At first the two different 30W-Cu materials were prepared by tungsten powder, copper powder and ultrafine tungsten-copper composite powder, and then the two materials’ formability were tested. Finally the material which had good formability was used to prepare EFP liner. It was found that the 30W-Cu material prepared by common tungsten powder and copper powder had a good formability. 98.2% of the theoretical density of the density of the 30W-Cu EFP liner material was obtained. After annealing, the tensile strength of the material reached 315 MPa and elongation reached 15.3%
The preparation and formability of 30W-Cu EFP(explosively formed projectile) liner were studied. At first the two different 30W-Cu materials were prepared by tungsten powder, copper powder and ultrafine tungsten-copper composite powder, and then the two materials’ formability were tested. Finally the material which had good formability was used to prepare EFP liner. It was found that the 30W-Cu material prepared by common tungsten powder and copper powder had a good formability. 98.2% of the theoretical density of the density of the 30W-Cu EFP liner material was obtained. After annealing, the tensile strength of the material reached 315 MPa and elongation reached 15.3%
2009, 38(9):1622-1625.
Abstract:
Using the MSC.Marc software, the temperature and stress fields in beryllium during cutting process are studied by employing a thermo-mechanically coupled finite element method (FEM). The constitutive equation of beryllium is fitted with the Johnson-Cook plasticity model, and an user subroutine is written for modeling the chip separation after fracturing. The results show that the temperature in beryllium increases only a little and the highest temperature is about 45 ℃. Both of the residual stress components for parallel and vertical to the cutting direction are tensile on the surface of beryllium after cutting. The cutting force and thrust force are 280 and –250 N/mm, respectively, during the cutting steady state if the cutting process is adopted in this paper. This study is helpful to enhance the understanding for stress formation and the optimizing for the beryllium cutting process.
Using the MSC.Marc software, the temperature and stress fields in beryllium during cutting process are studied by employing a thermo-mechanically coupled finite element method (FEM). The constitutive equation of beryllium is fitted with the Johnson-Cook plasticity model, and an user subroutine is written for modeling the chip separation after fracturing. The results show that the temperature in beryllium increases only a little and the highest temperature is about 45 ℃. Both of the residual stress components for parallel and vertical to the cutting direction are tensile on the surface of beryllium after cutting. The cutting force and thrust force are 280 and –250 N/mm, respectively, during the cutting steady state if the cutting process is adopted in this paper. This study is helpful to enhance the understanding for stress formation and the optimizing for the beryllium cutting process.
2017, 46(3):612-616.
Abstract:
In order to solve the wear repair problem of large steam turbine rotor shaft journal, the material of steam turbine rotor shaft as substrate and the self-made special laser cladding remanufacturing powder as experimental material, the experiments were carried out by laser cladding remanufacturing method based on laser cladding remanufacturing system with coaxial powder feeder. Focusing on effect of different width of laser cladding layers on total indicated runout (TIR) of steam turbine rotor, the experiment research and mechanism simulation verification were performed, and the influence mechanism of different factors were analyzed. The results show that the data results of total indicated runout are closely related to probe diameter and laser cladding layer width. The width of cladding layer determines the turbine rotor surface magnetic, eddy current density and magnetic flux density distribution. Due to the interference of matrix magnetic field and eddy current density of surface, the magnetic flux density suddenly changes in the laser cladding layer edge when the laser cladding layer width is less than 8mm.The measurement results are too large caused by the comprehensive effect of substrate and laser cladding layer. According to the numerical simulation of magnetic flux density distribution of measured metal body surface, the critical value of laser cladding width is 9.82mm.
In order to solve the wear repair problem of large steam turbine rotor shaft journal, the material of steam turbine rotor shaft as substrate and the self-made special laser cladding remanufacturing powder as experimental material, the experiments were carried out by laser cladding remanufacturing method based on laser cladding remanufacturing system with coaxial powder feeder. Focusing on effect of different width of laser cladding layers on total indicated runout (TIR) of steam turbine rotor, the experiment research and mechanism simulation verification were performed, and the influence mechanism of different factors were analyzed. The results show that the data results of total indicated runout are closely related to probe diameter and laser cladding layer width. The width of cladding layer determines the turbine rotor surface magnetic, eddy current density and magnetic flux density distribution. Due to the interference of matrix magnetic field and eddy current density of surface, the magnetic flux density suddenly changes in the laser cladding layer edge when the laser cladding layer width is less than 8mm.The measurement results are too large caused by the comprehensive effect of substrate and laser cladding layer. According to the numerical simulation of magnetic flux density distribution of measured metal body surface, the critical value of laser cladding width is 9.82mm.
2009, 38(2):365-367.
Abstract:
The Mg-8 mol% LaNi0.5 hydrogen storage materials were prepared by mechanically milling at cryogenic temperature (cryomilling). The phase structure and surface morphology of the materials were studied by XRD and SEM, the granularity distribution was determined by laser method, the hydrogen storage performance of the materials were studied by an equipment of PCT (pressure-composition-Temperature). The results showed that a small amount of the alloy phase appeared after ten hours. The average particle size of the materials is 10 μm. The materials had a flat platform of hydrogen absorption and desorption, the hydrogen storage capacity is 2.33 wt% at 573 K. Under 4.0 MPa hydrogen pressure, the materials can absorb more than 80% of their full hydrogen capacity in 3 min to 5 min at 523 K~653 K. The materials prepared by cryomilling had better activation performance, without activation, and fine platform performance, and the dynamic performance was improved
The Mg-8 mol% LaNi0.5 hydrogen storage materials were prepared by mechanically milling at cryogenic temperature (cryomilling). The phase structure and surface morphology of the materials were studied by XRD and SEM, the granularity distribution was determined by laser method, the hydrogen storage performance of the materials were studied by an equipment of PCT (pressure-composition-Temperature). The results showed that a small amount of the alloy phase appeared after ten hours. The average particle size of the materials is 10 μm. The materials had a flat platform of hydrogen absorption and desorption, the hydrogen storage capacity is 2.33 wt% at 573 K. Under 4.0 MPa hydrogen pressure, the materials can absorb more than 80% of their full hydrogen capacity in 3 min to 5 min at 523 K~653 K. The materials prepared by cryomilling had better activation performance, without activation, and fine platform performance, and the dynamic performance was improved
2009, 38(8):1317-1320.
Abstract:
A 3D thermal elastic-plastic finite element model to predict welding residual stresses induced by full-penetration laser welding of Ti6Al4V alloy was described in detail. The welding experiments and residual stresses measurements by through-thickness hole-drilling method were also performed to validate the simulated results. A uniform conical heat source model with parameters taken from the actual weld seam dimensions was developed to simulate the welding temperature fields with different welding heat inputs. The thermal elastic-plastic finite element simulation was employed to calculate the welding residual stresses. The boundary conditions and the size of finite element mesh were also discussed. The results show that the cross section profiles of the weld seam simulated with the conical heat source based on the configuration of weld seam agree well with the experimental results; the zone of residual stresses distribution in laser full-penetration welding of Ti6Al4V alloy is very narrow and the gradient of longitudinal residual stress is very steep; the residual stresses distribution on the surfaces are different from those in the interior of the welding seam; the measured residual stresses by through-thickness hole-drilling method are similar to the simulated ones in the interior of the welding seam.
A 3D thermal elastic-plastic finite element model to predict welding residual stresses induced by full-penetration laser welding of Ti6Al4V alloy was described in detail. The welding experiments and residual stresses measurements by through-thickness hole-drilling method were also performed to validate the simulated results. A uniform conical heat source model with parameters taken from the actual weld seam dimensions was developed to simulate the welding temperature fields with different welding heat inputs. The thermal elastic-plastic finite element simulation was employed to calculate the welding residual stresses. The boundary conditions and the size of finite element mesh were also discussed. The results show that the cross section profiles of the weld seam simulated with the conical heat source based on the configuration of weld seam agree well with the experimental results; the zone of residual stresses distribution in laser full-penetration welding of Ti6Al4V alloy is very narrow and the gradient of longitudinal residual stress is very steep; the residual stresses distribution on the surfaces are different from those in the interior of the welding seam; the measured residual stresses by through-thickness hole-drilling method are similar to the simulated ones in the interior of the welding seam.
2009, 38(8):1422-1425.
Abstract:
The mechanical properties at room and elevated temperature as well as the friction wear behavior under dry sliding condition for as-cast Mg97Zn1Y2 alloy were investigated, and compared with that of AZ91 alloy. The results show that the yield strength of AZ91 alloy is higher than that of Mg97Zn1Y2 alloy at room temperature, but Mg97Zn1Y2 alloy exhibits better thermal stability at the evaluated temperature; as the temperature is above 150 ℃, the yield strength of AZ91 alloy decreases sharply, but that of Mg97Zn1Y2 alloy decreases a little. The transition point from mild wear to severe wear for Mg97Zn1Y2 alloy obviously lags that of AZ91 alloy. In the same load range, the bulk temperature rise of wear surface of the Mg97Zn1Y2 alloy is also lower than that of AZ91 alloy. The reason is that the intermetallic compound Mg12YZn in Mg97Zn1Y2 alloy possesses better thermal stability than Mg17Al12 phase in AZ91 alloy.
The mechanical properties at room and elevated temperature as well as the friction wear behavior under dry sliding condition for as-cast Mg97Zn1Y2 alloy were investigated, and compared with that of AZ91 alloy. The results show that the yield strength of AZ91 alloy is higher than that of Mg97Zn1Y2 alloy at room temperature, but Mg97Zn1Y2 alloy exhibits better thermal stability at the evaluated temperature; as the temperature is above 150 ℃, the yield strength of AZ91 alloy decreases sharply, but that of Mg97Zn1Y2 alloy decreases a little. The transition point from mild wear to severe wear for Mg97Zn1Y2 alloy obviously lags that of AZ91 alloy. In the same load range, the bulk temperature rise of wear surface of the Mg97Zn1Y2 alloy is also lower than that of AZ91 alloy. The reason is that the intermetallic compound Mg12YZn in Mg97Zn1Y2 alloy possesses better thermal stability than Mg17Al12 phase in AZ91 alloy.
2015, 44(3):768-774.
Abstract:
Precipitation strengthening Ni-Fe based superalloy GH4169 has been widely used in aircraft engine, petroleum, nuclear industrial etc. Previous papers indicated that the phase transition from γ" to δ was performed when the temperature exceeded 650 oC. The reduction of strengthening phase amount degraded the mechanical properties and the application range. This paper summarized the characteristics of composition, microstructure and precipitated phases of GH4169 alloy. The influences of heat treatment and heat deformation process on the stability of microstructure and mechanical properties were reviewed, and the mechanical properties were affected by the morphologies and distribution of δ phase. The composition features of the modified alloy were concluded. In addition, the future trends and the possibility of GH4169 alloy to satisfy the use requirement for the 700 oC advanced ultra-supercritical power plants were proposed.
Precipitation strengthening Ni-Fe based superalloy GH4169 has been widely used in aircraft engine, petroleum, nuclear industrial etc. Previous papers indicated that the phase transition from γ" to δ was performed when the temperature exceeded 650 oC. The reduction of strengthening phase amount degraded the mechanical properties and the application range. This paper summarized the characteristics of composition, microstructure and precipitated phases of GH4169 alloy. The influences of heat treatment and heat deformation process on the stability of microstructure and mechanical properties were reviewed, and the mechanical properties were affected by the morphologies and distribution of δ phase. The composition features of the modified alloy were concluded. In addition, the future trends and the possibility of GH4169 alloy to satisfy the use requirement for the 700 oC advanced ultra-supercritical power plants were proposed.
2016, 45(7):1719-1725.
Abstract:
Abstract: The influence of Ru element on the creep properties under 1120 ℃/140 MPa of high Re Ni-based single crystal superalloys with two levels of Ru (0, 2wt.%) additions was investigated. The γ/γ′ phase, partitioning ratio of alloying elements, deformation microstructures and the morphology of dislocations were studied by SEM, STEM/TEM and EDS. The results indicate that Ru addition results in decreasing the size of γ′ phase, width of γ channel and elemental partitioning ratio of Re，Mo and Cr which are important for the precipitation of TCP phase. Ru addition decreased the size of γ′ phase and width of γ channel, decreased the spacing of γ/γ′ interfacial dislocation networks and inhibited the precipitation of TCP phase in the process of creep loading, finally improving the creep properties of the investigatived alloy significantly. This study would be helpful for the understanding of ruthenium’s role of strengthening mechanism in high temperature creep of Ni-base single crystal superalloys. Key words: single crystal superalloys; Ru; micrstructures; partitioning of elements in γ/γ′ phase; creep properties
Abstract: The influence of Ru element on the creep properties under 1120 ℃/140 MPa of high Re Ni-based single crystal superalloys with two levels of Ru (0, 2wt.%) additions was investigated. The γ/γ′ phase, partitioning ratio of alloying elements, deformation microstructures and the morphology of dislocations were studied by SEM, STEM/TEM and EDS. The results indicate that Ru addition results in decreasing the size of γ′ phase, width of γ channel and elemental partitioning ratio of Re，Mo and Cr which are important for the precipitation of TCP phase. Ru addition decreased the size of γ′ phase and width of γ channel, decreased the spacing of γ/γ′ interfacial dislocation networks and inhibited the precipitation of TCP phase in the process of creep loading, finally improving the creep properties of the investigatived alloy significantly. This study would be helpful for the understanding of ruthenium’s role of strengthening mechanism in high temperature creep of Ni-base single crystal superalloys. Key words: single crystal superalloys; Ru; micrstructures; partitioning of elements in γ/γ′ phase; creep properties
2009, 38(12):2226-2229.
Abstract:
Ti6Al4V alloy surface was multi-alloyed by a double-glow plasma technique, and the homogeneous and dense Cr-Mo modified layer was formed. The phase structure and composition of the modified layer was characterized by XRD and GDOES, and its properties were tested by microhardness meter and ball-plate wear instrument. The results show that the composition in the modified layer are Cr and a few Mo, and decrease gradually from the surface to the underlying substrate. The layer is composed of Cr1.93Ti1.07, Cr2Ti, Cr2Ti4O11 and a few FeCrMo phase. Surface hardness of the modified Ti6Al4V alloy is increased greatly, and the wear resistance is improved significantly.
Ti6Al4V alloy surface was multi-alloyed by a double-glow plasma technique, and the homogeneous and dense Cr-Mo modified layer was formed. The phase structure and composition of the modified layer was characterized by XRD and GDOES, and its properties were tested by microhardness meter and ball-plate wear instrument. The results show that the composition in the modified layer are Cr and a few Mo, and decrease gradually from the surface to the underlying substrate. The layer is composed of Cr1.93Ti1.07, Cr2Ti, Cr2Ti4O11 and a few FeCrMo phase. Surface hardness of the modified Ti6Al4V alloy is increased greatly, and the wear resistance is improved significantly.
56 Globularization Mechanisms during Hot Deformation Processes of TC11 Alloy with Lamellar Structure
2009, 38(3):421-425.
Abstract:
Microstructure and grain boundary character during hot deformation globularization processes of TC11 alloy with annealed-lamellar structure were investigated by TEM, SEM and EBSD techniques. The results indicate that globularization processes include: 1) forming of sub-structures with low-angle boundaries by deformation and recovery in α plates; 2) disintegrating of α plates by diffusion and slipping along grain boundaries; 3) globularizing of α grains and homogenizing of structure by diffusing and slipping along grain boundaries. EBSD testing results indicate that globularization mechanisms during hot deformation processes of the alloy with lamellar structure are continuous dynamic recrystallization occurring in α plates and dynamic recovery or discontinuous dynamic recrystallization occurring in β phase
Microstructure and grain boundary character during hot deformation globularization processes of TC11 alloy with annealed-lamellar structure were investigated by TEM, SEM and EBSD techniques. The results indicate that globularization processes include: 1) forming of sub-structures with low-angle boundaries by deformation and recovery in α plates; 2) disintegrating of α plates by diffusion and slipping along grain boundaries; 3) globularizing of α grains and homogenizing of structure by diffusing and slipping along grain boundaries. EBSD testing results indicate that globularization mechanisms during hot deformation processes of the alloy with lamellar structure are continuous dynamic recrystallization occurring in α plates and dynamic recovery or discontinuous dynamic recrystallization occurring in β phase
57 The formation and influence mechanism as well as experimental characterization of composite porosity
2016, 45(9):2282-2286.
Abstract:
In view of the common issue of composite porosity, the formation and influence mechanism of composite porosity are elucidated from the aspects of mechanical mixed nucleation theory and classic nucleation theory. The characterization of porosity morphology, distribution and size are conducted through specific test. The results show that: poor wettability of fibers, retention of vapor molecules and molecular volatilization generated during the crosslinking reaction are the main reasons of porosity formation. The lower cure pressures have a little effect on eliminating the porosity. With the increase of cure pressure, the porosity factor and porosity size decrease significantly. With the method of data fitting, the relations of porosity factor, porosity diameter and cure pressure are obtained, and the power function relations of three times are existed among them. This paper provides a theoretical and experimental support for optimizing the design of composites manufacturing process.
In view of the common issue of composite porosity, the formation and influence mechanism of composite porosity are elucidated from the aspects of mechanical mixed nucleation theory and classic nucleation theory. The characterization of porosity morphology, distribution and size are conducted through specific test. The results show that: poor wettability of fibers, retention of vapor molecules and molecular volatilization generated during the crosslinking reaction are the main reasons of porosity formation. The lower cure pressures have a little effect on eliminating the porosity. With the increase of cure pressure, the porosity factor and porosity size decrease significantly. With the method of data fitting, the relations of porosity factor, porosity diameter and cure pressure are obtained, and the power function relations of three times are existed among them. This paper provides a theoretical and experimental support for optimizing the design of composites manufacturing process.
2016, 45(9):2219-2226.
Abstract:
Based on the central composite rotatable design (CCD), clad beads of Inconel 625 were deposited on the surface of AISI 4130 plates using hot wire pulsed TIG technology. The response surface methodology (RSM) was utilized to establish models between process parameters and geometrical characteristics of the clad beads. Then, multiple-track two-layer weld overlay was successfully deposited using the optimized process parameters. The microstructure of the weld overlay is primarily composed of columnar dendrites, and there are also a few planar crystals and cellular dendrites situated near the fusion zone. Meanwhile, equiaxed grains and steering dendrites are mainly distributed in the upper portion of the weld overlay. Potentiodynamic polarization tests were used to evaluate the corrosion resistance of the weld overlay and substrate. The results show that adding clad layers can enhance the corrosion resistance, which degrades with the increase in Fe dilution. Moreover, the corrosion resistance of the second layer surface is close to that of wrought Inconel 625.
Based on the central composite rotatable design (CCD), clad beads of Inconel 625 were deposited on the surface of AISI 4130 plates using hot wire pulsed TIG technology. The response surface methodology (RSM) was utilized to establish models between process parameters and geometrical characteristics of the clad beads. Then, multiple-track two-layer weld overlay was successfully deposited using the optimized process parameters. The microstructure of the weld overlay is primarily composed of columnar dendrites, and there are also a few planar crystals and cellular dendrites situated near the fusion zone. Meanwhile, equiaxed grains and steering dendrites are mainly distributed in the upper portion of the weld overlay. Potentiodynamic polarization tests were used to evaluate the corrosion resistance of the weld overlay and substrate. The results show that adding clad layers can enhance the corrosion resistance, which degrades with the increase in Fe dilution. Moreover, the corrosion resistance of the second layer surface is close to that of wrought Inconel 625.
2015, 44(3):603-607.
Abstract:
Thermal stress and optimum structure design of tungsten/copper functional gradient materials (W/Cu FGM) were analyzed via ANSYS12.0 code. The results show that the maximum thermal stresses firstly decrease to a bottom value and then slightly increase with the increasing of compositional exponent (p) of W/Cu FGM. The equivalent Von Mises thermal stress for the W/Cu FGM (p=1.3) is 180 MPa, decreased by 79% compared with non-FGM under heat flux of 30 MW/m2. According to the simulation results, the optimal parameters of the W/Cu FGM are listed as following: above 3 mm for the thickness, 4~6 layer for the W/Cu FGM and 1 mm to 3 mm of the thickness for the tungsten layer.
Thermal stress and optimum structure design of tungsten/copper functional gradient materials (W/Cu FGM) were analyzed via ANSYS12.0 code. The results show that the maximum thermal stresses firstly decrease to a bottom value and then slightly increase with the increasing of compositional exponent (p) of W/Cu FGM. The equivalent Von Mises thermal stress for the W/Cu FGM (p=1.3) is 180 MPa, decreased by 79% compared with non-FGM under heat flux of 30 MW/m2. According to the simulation results, the optimal parameters of the W/Cu FGM are listed as following: above 3 mm for the thickness, 4~6 layer for the W/Cu FGM and 1 mm to 3 mm of the thickness for the tungsten layer.
60 Comparison of Ru-Ti-Ir-Ta/Ti Quarternary Coating Prepared by Different Techniques on Titanium Anodes
2009, 38(10):1843-1847.
Abstract:
Ru-Ti-Ir-Ta/Ti quarternary metal oxide titanium anodes with sandwich coating structure were prepared by thermal decomposition and sol-gel method, respectively. The phases and micro-morphologies of the two coatings were investigated by means of XRD and SEM. The electrocatalytic activity of the coatings was studied and compared by Tafel curve and cyclic voltammetry curve. It is demonstrated that the main phases in the coatings prepared by different techniques are mainly rutile-type solid solution (Ir, Ta)O2 and (Ti, Ru)O2. Metallic Ru is found in the coating prepared by thermal decomposition. The crystals in the coating prepared by sol-gel are finer. The morphologies of the coatings by thermal decomposition and sol-gel are obviously different. The former is distinctly dry cracked-mud like, and the latter shows the detritus-type. The result indicates that the titanium anode prepared by sol-gel have the better electrocatalytic activity and corrosion resistance than that by thermal decomposition.
Ru-Ti-Ir-Ta/Ti quarternary metal oxide titanium anodes with sandwich coating structure were prepared by thermal decomposition and sol-gel method, respectively. The phases and micro-morphologies of the two coatings were investigated by means of XRD and SEM. The electrocatalytic activity of the coatings was studied and compared by Tafel curve and cyclic voltammetry curve. It is demonstrated that the main phases in the coatings prepared by different techniques are mainly rutile-type solid solution (Ir, Ta)O2 and (Ti, Ru)O2. Metallic Ru is found in the coating prepared by thermal decomposition. The crystals in the coating prepared by sol-gel are finer. The morphologies of the coatings by thermal decomposition and sol-gel are obviously different. The former is distinctly dry cracked-mud like, and the latter shows the detritus-type. The result indicates that the titanium anode prepared by sol-gel have the better electrocatalytic activity and corrosion resistance than that by thermal decomposition.
2009, 38(6):1033-1037.
Abstract:
The stable precursor slurry of indium-tin-oxide (ITO) was prepared using metal In and crystalloid tin tetrachloride as raw materials by adding different additives. The effect of dispersants on the stability of ITO precursor slurry was studied by Zeta potential value, TEM and sediment. The influences of pH value and dispersant content on stability of the slurry were investigated. And the effects of the different dispersant and their dispersing mechanism on the stability of the slurry were also investigated. The results show that a higher electrostatic effect could be obtained by adjusting pH value of medium and adding ionic dispersant. Based on the above mentioned, non-ionic surfactants (PEG, PVP) were added, resulting in creating a steric hindered effect among particles, which prevented the agglomeration of the particles so as to obtain a high dispersed and steady slurry. The particle sizes of the slurry were about 10~20 nm. The following finding can be drawn from the experiment that the optimum contents of dispersants are PEG 10% and monoethanolamine 2.5% (mass fraction).
The stable precursor slurry of indium-tin-oxide (ITO) was prepared using metal In and crystalloid tin tetrachloride as raw materials by adding different additives. The effect of dispersants on the stability of ITO precursor slurry was studied by Zeta potential value, TEM and sediment. The influences of pH value and dispersant content on stability of the slurry were investigated. And the effects of the different dispersant and their dispersing mechanism on the stability of the slurry were also investigated. The results show that a higher electrostatic effect could be obtained by adjusting pH value of medium and adding ionic dispersant. Based on the above mentioned, non-ionic surfactants (PEG, PVP) were added, resulting in creating a steric hindered effect among particles, which prevented the agglomeration of the particles so as to obtain a high dispersed and steady slurry. The particle sizes of the slurry were about 10~20 nm. The following finding can be drawn from the experiment that the optimum contents of dispersants are PEG 10% and monoethanolamine 2.5% (mass fraction).
2009, 38(2):299-302.
Abstract:
The La0.7Sr0.3MnO3/Nb-1wt%-doped SrTiO3 p-n junction fabricated by the magnetron sputtering technique exhibits excellent rectifying characteristics over the temperature range from 40 to 320 K, nearly independent of the temperature. The modulated electromagnetic property of La0.7Sr0.3MnO3 is also achieved by the built-in electric field near the interface of junction. The diffusion potential decreases almost linearly with increasing the temperatures. It can be understood by considering a picture that the depletion layer in p-n junction becomes thinner and thinner with the increase of temperature due to the thermal diffusion effect. In addition, this phenomenon is also attributed to the variation of the electronic structure of LSMO with temperature increasing. The junction resistance decreases sharply when the applied forward current increases from 1 mA to 50 mA while the insulator-metal transition temperature TP increases from around 200 K to 250 K due to the strength enhancement of the ferromagnetic double-exchange interaction
The La0.7Sr0.3MnO3/Nb-1wt%-doped SrTiO3 p-n junction fabricated by the magnetron sputtering technique exhibits excellent rectifying characteristics over the temperature range from 40 to 320 K, nearly independent of the temperature. The modulated electromagnetic property of La0.7Sr0.3MnO3 is also achieved by the built-in electric field near the interface of junction. The diffusion potential decreases almost linearly with increasing the temperatures. It can be understood by considering a picture that the depletion layer in p-n junction becomes thinner and thinner with the increase of temperature due to the thermal diffusion effect. In addition, this phenomenon is also attributed to the variation of the electronic structure of LSMO with temperature increasing. The junction resistance decreases sharply when the applied forward current increases from 1 mA to 50 mA while the insulator-metal transition temperature TP increases from around 200 K to 250 K due to the strength enhancement of the ferromagnetic double-exchange interaction
2016, 45(8):2139-2145.
Abstract:
A novel electroactive α-ZrP/PANI hybrid film with cation exchange property was synthesized by electrochemical method in aqueous solution. The electrochemically switched ion exchange capacity of this film was investigated in 0.1 M Pb(NO3)2. The α-ZrP/PANI hybrid films with different structures were prepared on carbon nanotubes (CNTs) and PANI nanofibers modified Au electrodes. The fabrication process and formation mechanism were analyzed by electrochemical quartz crystal microbalance (EQCM). The results shows that the hybrid film prepared on PANI fibers exhibited higher ion exchange capacity because of its three-dimensional porous structure; The P-OH of α-ZrP not only provides protons for the redox of PANI but also shows adsorption selectivity for Pb2 , which makes this hybrid film perform good electroactivity in neutral solution containing Pb2 . Therefore, this hybrid film could be served as an ESIX material for separation and recovery of Pb2 by controlling the oxidation-reduction of hybrid film.
A novel electroactive α-ZrP/PANI hybrid film with cation exchange property was synthesized by electrochemical method in aqueous solution. The electrochemically switched ion exchange capacity of this film was investigated in 0.1 M Pb(NO3)2. The α-ZrP/PANI hybrid films with different structures were prepared on carbon nanotubes (CNTs) and PANI nanofibers modified Au electrodes. The fabrication process and formation mechanism were analyzed by electrochemical quartz crystal microbalance (EQCM). The results shows that the hybrid film prepared on PANI fibers exhibited higher ion exchange capacity because of its three-dimensional porous structure; The P-OH of α-ZrP not only provides protons for the redox of PANI but also shows adsorption selectivity for Pb2 , which makes this hybrid film perform good electroactivity in neutral solution containing Pb2 . Therefore, this hybrid film could be served as an ESIX material for separation and recovery of Pb2 by controlling the oxidation-reduction of hybrid film.
2009, 38(9):1602-1607.
Abstract:
The microstructure and mechanical properties of AlxCoCrCuFeNi with different Al content have been studied. The results showed that the microstructures exhibit simple dendrite and interdendrite structures. When the content of aluminum was low, the alloy was composed of a simple FCC solid-solution structure. As the aluminum contents increasing, a BCC structure appeared. The high entropy effects and sluggish diffusion enhance the formation of simple solid-solution phases and submicron structures with nanoprecipitates in the alloys. With the addition of aluminum from x=0 to 3.0, the hardness of the alloys increase from 1530 to 7350 MPa Correspondingly, the alloy’s deformability falls and transfers from ductile materials to brittle materials at moderate temperatures.
The microstructure and mechanical properties of AlxCoCrCuFeNi with different Al content have been studied. The results showed that the microstructures exhibit simple dendrite and interdendrite structures. When the content of aluminum was low, the alloy was composed of a simple FCC solid-solution structure. As the aluminum contents increasing, a BCC structure appeared. The high entropy effects and sluggish diffusion enhance the formation of simple solid-solution phases and submicron structures with nanoprecipitates in the alloys. With the addition of aluminum from x=0 to 3.0, the hardness of the alloys increase from 1530 to 7350 MPa Correspondingly, the alloy’s deformability falls and transfers from ductile materials to brittle materials at moderate temperatures.
Xue Guanxia
,
Wang Tongmin
,
Su Yanqing
,
Cai Shaowu
,
Xu Jingjing
,
Li Jun
,
Guo Jingjie
,
Li Tingju
2009, 38(5):761-765.
Abstract:
The electromagnetic, thermal and fluid fields during ISM (Induction Skull Melting)of TiAl alloy are simulated. The effects of ampere-turn, frequency and relative position between crucible and coil on the distribution of thermal and flow fields are numerically studied. The simulation model is verified by experiments and the simulation results are discussed in detail
The electromagnetic, thermal and fluid fields during ISM (Induction Skull Melting)of TiAl alloy are simulated. The effects of ampere-turn, frequency and relative position between crucible and coil on the distribution of thermal and flow fields are numerically studied. The simulation model is verified by experiments and the simulation results are discussed in detail
2009, 38(2):281-285.
Abstract:
Supersaturated CuCr solid solution was prepared by pulverization. After that, the aging dynamics were analyzed at different temperatures. The results showed that the G.P zone was presented at relatively low temperature. We could observe a coherent interface between precipitated phase and matrix. The results that were obtained both from transmission electron microscope (TEM) and Electron Energy Disperse Spectroscopy (EDS) revealed that as aging time increased, the amount of Cr metal phase also increased due to solute enrichment process. On the other hand, the activation energy for atomic diffusion was reduced at high temperature. As a result, the metal phases of Cr were formed very fast. The fractional volume of the precipitated phase was measured by EDS and then applied Avrami equation to analyze the dynamical effect of aging. Finally we concluded that the phase transition in CuCr alloy was determined by aging dynamics and diffusion was the most important effect of aging process, other factors such as solute species, impurities, vacancies, dislocations, grain boundaries and lattice distortions may be affected this process, too.
Supersaturated CuCr solid solution was prepared by pulverization. After that, the aging dynamics were analyzed at different temperatures. The results showed that the G.P zone was presented at relatively low temperature. We could observe a coherent interface between precipitated phase and matrix. The results that were obtained both from transmission electron microscope (TEM) and Electron Energy Disperse Spectroscopy (EDS) revealed that as aging time increased, the amount of Cr metal phase also increased due to solute enrichment process. On the other hand, the activation energy for atomic diffusion was reduced at high temperature. As a result, the metal phases of Cr were formed very fast. The fractional volume of the precipitated phase was measured by EDS and then applied Avrami equation to analyze the dynamical effect of aging. Finally we concluded that the phase transition in CuCr alloy was determined by aging dynamics and diffusion was the most important effect of aging process, other factors such as solute species, impurities, vacancies, dislocations, grain boundaries and lattice distortions may be affected this process, too.
67 Growth Behavior of Cu6Sn5 at the Interface of Sn-2.5Ag-0.7Cu(0.1RE) Solder Joints for Micro-Joining
2010, 39(1):117-121.
Abstract:
The microstructure of low-Ag-content Sn-2.5Ag-0.7Cu(0.1RE)/Cu solder joint interface and growth behavior of Cu6Sn5 intermetallic compound (IMC) were investigated by XRD, SEM and EDAX. The results show that the Cu6Sn5 thickness of the solder joint interface is decided by its dissolution and growing during soldering. With the aging time increasing, the Cu6Sn5 morphology of the solder joint interface changed from scallop-like to lamellar; the growth dynamics follows the parabola law and its growth behavior is controlled by diffusion mechanism. Addition of 0.1% RE (mass fraction) in the Sn-2.5Ag-0.7Cu solder alloy can effectively reduce the growing rate of the solder joint Cu6Sn5 IMC during the soldering and aging period, and change the fracture mechanism of solder joint; therefore the reliability of the solder joint can be greatly improved.
The microstructure of low-Ag-content Sn-2.5Ag-0.7Cu(0.1RE)/Cu solder joint interface and growth behavior of Cu6Sn5 intermetallic compound (IMC) were investigated by XRD, SEM and EDAX. The results show that the Cu6Sn5 thickness of the solder joint interface is decided by its dissolution and growing during soldering. With the aging time increasing, the Cu6Sn5 morphology of the solder joint interface changed from scallop-like to lamellar; the growth dynamics follows the parabola law and its growth behavior is controlled by diffusion mechanism. Addition of 0.1% RE (mass fraction) in the Sn-2.5Ag-0.7Cu solder alloy can effectively reduce the growing rate of the solder joint Cu6Sn5 IMC during the soldering and aging period, and change the fracture mechanism of solder joint; therefore the reliability of the solder joint can be greatly improved.
2017, 46(1):207-212.
Abstract:
The nano-cooper powder and graphene are mixed by the way of mechanical wet ball-milling. Then the graphene/cooper (G/Cu) composite materials is prepared by the Spark Plasma Sintering method(SPS). The microstructure and organization structure of graphene and cooper power are analyzed by means of SEM, XRD and other test methods to explore the relationship between the variation of graphene and cooper power and the ball-milling process. It has found that when the ball-milling time increased to 8h, the grapnene nanoplates have a better combination and distribution on cooper substrate. The improvement of performance is relatively best. The tensile yield strength of the G/Cu composite is 183MPa, increased by 52.5%compared with Cu matrix; the compres yield strength is improve more nearly 1.4 times from 150MPa to 365Mpa; the hardness is also increased to 135HV; the conductivity IACS of the composites reaches 65.5%. The comprehensive performance increased significantly.
The nano-cooper powder and graphene are mixed by the way of mechanical wet ball-milling. Then the graphene/cooper (G/Cu) composite materials is prepared by the Spark Plasma Sintering method(SPS). The microstructure and organization structure of graphene and cooper power are analyzed by means of SEM, XRD and other test methods to explore the relationship between the variation of graphene and cooper power and the ball-milling process. It has found that when the ball-milling time increased to 8h, the grapnene nanoplates have a better combination and distribution on cooper substrate. The improvement of performance is relatively best. The tensile yield strength of the G/Cu composite is 183MPa, increased by 52.5%compared with Cu matrix; the compres yield strength is improve more nearly 1.4 times from 150MPa to 365Mpa; the hardness is also increased to 135HV; the conductivity IACS of the composites reaches 65.5%. The comprehensive performance increased significantly.
2009, 38(9):1509-1513.
Abstract:
The diffusion bonding of TC21 titanium alloy with initial grain size of 2 μm was performed at 780-980 oC for 5-90 min. The microstructure, bonding quality, microhardness and deformation ratio of the joints were analyzed. It is found that the interface bonding ratio can achieve 100% and the deformation ratio can be controlled within 10% when diffusion bonding is performed at 880 oC for 15-30 min. The microhardness of the joints increases with increasing of bonding temperature, but it shows a peak value as the bonding time is prolonged. When the joint is bonded at 880-930 oC, fully equiaxed structures are observed, and with increasing of bonding temperature, the sizes of α and β phases are increased; but when bonding temperature is up to 980 ℃, fully lamellar structures are obtained. When the joint is bonded at 880 oC for 5-60 min, the size of α and β phases increases with prolonging of bonding time. However, when the bonding time is prolonged to 90 min, the sizes of α and β phases decrease slightly
The diffusion bonding of TC21 titanium alloy with initial grain size of 2 μm was performed at 780-980 oC for 5-90 min. The microstructure, bonding quality, microhardness and deformation ratio of the joints were analyzed. It is found that the interface bonding ratio can achieve 100% and the deformation ratio can be controlled within 10% when diffusion bonding is performed at 880 oC for 15-30 min. The microhardness of the joints increases with increasing of bonding temperature, but it shows a peak value as the bonding time is prolonged. When the joint is bonded at 880-930 oC, fully equiaxed structures are observed, and with increasing of bonding temperature, the sizes of α and β phases are increased; but when bonding temperature is up to 980 ℃, fully lamellar structures are obtained. When the joint is bonded at 880 oC for 5-60 min, the size of α and β phases increases with prolonging of bonding time. However, when the bonding time is prolonged to 90 min, the sizes of α and β phases decrease slightly
2015, 44(7):1648-16542014-7-20.
Abstract:
In order to study the interdiffusion between Pd and Ti at high temperatures in a short time, the Pd coating was prepared on the surface of C.P.Ti by the magnetron sputtering technique. The Pd/Ti samples were heat-treated at 500, 550, 600 and 700 °C for 5 h. The phase composition, microstructure and element distribution of alloy layers were studied by XRD, SEM and EDS. The result shows that after the Pd/Ti sample is heat-treated at 500 °C for 5 h, a very slight interdiffusion occurs between Pd and Ti. When the temperature rises to 550 °C, a continuous diffusion layer appears between Pd coating and the substrate. As the temperature increases further, the interdiffusion becomes more and more obvious. When the temperature rises to 700 °C, TiPd3, TiPd2, Ti2Pd3, TiPd and Ti2Pd compound phases are observed on the alloyed surface layer. This paper also analyzed the Pd/Ti interface diffusion and reaction kinetics. The results indicate that increase of diffusion layer thickness experiences a process from interface reaction control to diffusion control.
In order to study the interdiffusion between Pd and Ti at high temperatures in a short time, the Pd coating was prepared on the surface of C.P.Ti by the magnetron sputtering technique. The Pd/Ti samples were heat-treated at 500, 550, 600 and 700 °C for 5 h. The phase composition, microstructure and element distribution of alloy layers were studied by XRD, SEM and EDS. The result shows that after the Pd/Ti sample is heat-treated at 500 °C for 5 h, a very slight interdiffusion occurs between Pd and Ti. When the temperature rises to 550 °C, a continuous diffusion layer appears between Pd coating and the substrate. As the temperature increases further, the interdiffusion becomes more and more obvious. When the temperature rises to 700 °C, TiPd3, TiPd2, Ti2Pd3, TiPd and Ti2Pd compound phases are observed on the alloyed surface layer. This paper also analyzed the Pd/Ti interface diffusion and reaction kinetics. The results indicate that increase of diffusion layer thickness experiences a process from interface reaction control to diffusion control.
2009, 38(6):1084-1086.
Abstract:
Fabrication of Zirconia Nanotube Arrays by Anodization
Fabrication of Zirconia Nanotube Arrays by Anodization
2009, 38(5):766-769.
Abstract:
The effect of various catalysts, such as Ti, Ni, Fe, Ce(SO4)2 and LaCl3, on the reversibility of LiAlH4 was studied by Pressure-Content-Temperature (PCT) experiments. The result indicates that doping induces a marked decrease in the rate of hydrogen release. In addition, doping additives obviously decreases the initial temperature of LiAlH4 of hydrogen release except for doping with LaCl3. However, at the same time, the amount of hydrogen release also decreases. In the study on the hydrogen absorption of LiAlH4 doped with 1mol% Ni, 1mol% Ti, 1 mol% Ce(SO4)2 and 1mol%LaCl3 at 180 ℃ under about 8 MPa, it has been found that the sample doped with 1 mol% Ni presents the largest hydrogen absorption amount with about 0.97wt%.
The effect of various catalysts, such as Ti, Ni, Fe, Ce(SO4)2 and LaCl3, on the reversibility of LiAlH4 was studied by Pressure-Content-Temperature (PCT) experiments. The result indicates that doping induces a marked decrease in the rate of hydrogen release. In addition, doping additives obviously decreases the initial temperature of LiAlH4 of hydrogen release except for doping with LaCl3. However, at the same time, the amount of hydrogen release also decreases. In the study on the hydrogen absorption of LiAlH4 doped with 1mol% Ni, 1mol% Ti, 1 mol% Ce(SO4)2 and 1mol%LaCl3 at 180 ℃ under about 8 MPa, it has been found that the sample doped with 1 mol% Ni presents the largest hydrogen absorption amount with about 0.97wt%.
2009, 38(3):536-540.
Abstract:
Mg58Al42 hydrogen storage alloy was prepared by mechanical alloying (MA) method and its microstructural characteristics and electrochemical properties such as discharge capacities and corrosion mechanisms were investigated by XRD, PARM273A and M5210 electrochemical apparatus. The results show that the X-ray diffraction peaks have a deviation and broadening with increment of ball milling time because of fine grain size and internal stress. The discharge capacities of the present alloy increase at the beginning of ball milling and afterwards decrease with increment of ball milling, discharge capacity of which is biggest when it is milled for 20 h. There are passivation phenomena in potentiodynamic polarization curves. The corrosion current densities of the present alloy increase with time at the beginning of ball milling and afterwards decrease. The electrochemical impedance spectroscopies(EIS) of the present alloy are composed of single capacitive loop and electrode reaction is controlled by charge transfer at alloy/electrolyte interface. The CPE-T of alloy increases. It showed that the specific surface areas of the alloy increase with ball milling time
Mg58Al42 hydrogen storage alloy was prepared by mechanical alloying (MA) method and its microstructural characteristics and electrochemical properties such as discharge capacities and corrosion mechanisms were investigated by XRD, PARM273A and M5210 electrochemical apparatus. The results show that the X-ray diffraction peaks have a deviation and broadening with increment of ball milling time because of fine grain size and internal stress. The discharge capacities of the present alloy increase at the beginning of ball milling and afterwards decrease with increment of ball milling, discharge capacity of which is biggest when it is milled for 20 h. There are passivation phenomena in potentiodynamic polarization curves. The corrosion current densities of the present alloy increase with time at the beginning of ball milling and afterwards decrease. The electrochemical impedance spectroscopies(EIS) of the present alloy are composed of single capacitive loop and electrode reaction is controlled by charge transfer at alloy/electrolyte interface. The CPE-T of alloy increases. It showed that the specific surface areas of the alloy increase with ball milling time
2009, 38(2):266-270.
Abstract:
The first-principles based on the density functional theory was applied to calculate the structure parameters, bond units and electronic structure of the oxidation mechanism for the Pt-Zr solid solution under high oxygen atmosphere. The calculated conclusions show that the structure parameter of the Pt-Zr solid solution was changed by the oxidation reaction of Pt-Zr, so that the expansion along c axis is larger than the b and c axis in the Pt-Zr solid solution. As the oxidation of Zr is stronger than Pt, the electrons on the 4d orbit of Zr combine the electrons on the 2p orbit of O to bond and form the oxide of Zr, but Pt just acts as a bridge function during the wholly oxidize process. It is also found that our calculated results are in good agreement with the experimental phenomenon
The first-principles based on the density functional theory was applied to calculate the structure parameters, bond units and electronic structure of the oxidation mechanism for the Pt-Zr solid solution under high oxygen atmosphere. The calculated conclusions show that the structure parameter of the Pt-Zr solid solution was changed by the oxidation reaction of Pt-Zr, so that the expansion along c axis is larger than the b and c axis in the Pt-Zr solid solution. As the oxidation of Zr is stronger than Pt, the electrons on the 4d orbit of Zr combine the electrons on the 2p orbit of O to bond and form the oxide of Zr, but Pt just acts as a bridge function during the wholly oxidize process. It is also found that our calculated results are in good agreement with the experimental phenomenon
2016, 45(9):2214-2218.
Abstract:
Heterogeneous Cu2O/Cu nanoparticles are synthesized by colloidal chemistry approach using ascorbic acid as a reducing agent and polyvinylpyrrolidone as a surfactant. Morphology and structure of Cu2O/Cu nanoparticles are analyzed by SEM, XRD and N2 sorption technique. The catalytic performances of Cu2O/Cu nanoparticles for the degradation of methyl orange (MO) are investigated and reaction kinetics of MO degradation is also studied. The results show heterogeneous Cu2O/Cu nanoparticles display cobblestone-like morphology with ranging from 20 to 40 nm, which are slightly smaller in particle size and higher in BET surface areas than those of pure Cu2O. The Cu2O/Cu nanoparticles demonstrate good potential on degradation of MO because Cu nanoparticles in the Cu2O/Cu hererostructures promote the interfacial charge-transfer kinetics between Cu and Cu2O. High initial MO concentration not only produces low degree of MO degradation, but also increases the reaction time to reach equilibrium, and the degradation reactions follow the pseudo-first-order kinetics model. The Cu2O/Cu catalyst still demonstrates good catalytic activity after four photodegradation cycles of MO solutions.
Heterogeneous Cu2O/Cu nanoparticles are synthesized by colloidal chemistry approach using ascorbic acid as a reducing agent and polyvinylpyrrolidone as a surfactant. Morphology and structure of Cu2O/Cu nanoparticles are analyzed by SEM, XRD and N2 sorption technique. The catalytic performances of Cu2O/Cu nanoparticles for the degradation of methyl orange (MO) are investigated and reaction kinetics of MO degradation is also studied. The results show heterogeneous Cu2O/Cu nanoparticles display cobblestone-like morphology with ranging from 20 to 40 nm, which are slightly smaller in particle size and higher in BET surface areas than those of pure Cu2O. The Cu2O/Cu nanoparticles demonstrate good potential on degradation of MO because Cu nanoparticles in the Cu2O/Cu hererostructures promote the interfacial charge-transfer kinetics between Cu and Cu2O. High initial MO concentration not only produces low degree of MO degradation, but also increases the reaction time to reach equilibrium, and the degradation reactions follow the pseudo-first-order kinetics model. The Cu2O/Cu catalyst still demonstrates good catalytic activity after four photodegradation cycles of MO solutions.
2016, 45(2):261-266.
Abstract:
A simple and environmentally friendly method was developed for preparing colloidal silver nanoparticels in aqueous solutions using silver nitrate, sodium alginate and glucose as silver precursor, capping agents and reducing agents respectively. The formation of silver nanoparticles was observed by change of color from colorless to yellow. The silver nanoparticles were characterized by transmission electron microscopy (TEM), UV-visible spectroscopy (UV-vis) and X-ray diffraction (XRD). The TEM images showed that, the particles are small, well dispersed and spherical in shape with a narrow distribution from 3 nm to 12 nm. The XRD demonstrated that the obtained metallic nanoparticles are single crystalline silver nanoparticles. The effects of the reaction time, reaction temperature and the concentration of silver ion and reducing agent on the particle size were investigated by the UV-vis spectra. The present process is an excellent candidate for the preparation of silver nanoparticles because it is simple, pollutant free, inexpensive and easy to perform. The method may be extended to other noble metals, such as Au, Pd and Pt, for medicinal, industrial and technological applications.
A simple and environmentally friendly method was developed for preparing colloidal silver nanoparticels in aqueous solutions using silver nitrate, sodium alginate and glucose as silver precursor, capping agents and reducing agents respectively. The formation of silver nanoparticles was observed by change of color from colorless to yellow. The silver nanoparticles were characterized by transmission electron microscopy (TEM), UV-visible spectroscopy (UV-vis) and X-ray diffraction (XRD). The TEM images showed that, the particles are small, well dispersed and spherical in shape with a narrow distribution from 3 nm to 12 nm. The XRD demonstrated that the obtained metallic nanoparticles are single crystalline silver nanoparticles. The effects of the reaction time, reaction temperature and the concentration of silver ion and reducing agent on the particle size were investigated by the UV-vis spectra. The present process is an excellent candidate for the preparation of silver nanoparticles because it is simple, pollutant free, inexpensive and easy to perform. The method may be extended to other noble metals, such as Au, Pd and Pt, for medicinal, industrial and technological applications.
77 First-principle studies of AlCoCrCuFexNi high entropy alloys with the different mole fractions of Cu
2016, 45(3):635-639.
Abstract:
The structural properties, elastic properties, and the heat of formations for the high entropy alloys (HEAs) AlCoCrCuxFeNi were studied by density functional theory and plane-wave pseudopotental technique with generalized gradient approximation (GGA), the crystal structure was built with the Virtual Crystal Approximation (VCA). The calculated results indicate that the mass density of HEA AlCoCrCuxFeNi increases with the increasing mole fraction of Cu, the lattice parameter is the largest when the mole fraction of Cu is 1.5. The mechanical stability of the HEA AlCoCrCuxFeNi is nothing to do with the mole fraction of Cu. The heat of formation decreases with the increasing mole fraction of Cu, but the HEAs AlCoCrCuxFeNi are thermodynamically stable due to their negative heats of formation.
The structural properties, elastic properties, and the heat of formations for the high entropy alloys (HEAs) AlCoCrCuxFeNi were studied by density functional theory and plane-wave pseudopotental technique with generalized gradient approximation (GGA), the crystal structure was built with the Virtual Crystal Approximation (VCA). The calculated results indicate that the mass density of HEA AlCoCrCuxFeNi increases with the increasing mole fraction of Cu, the lattice parameter is the largest when the mole fraction of Cu is 1.5. The mechanical stability of the HEA AlCoCrCuxFeNi is nothing to do with the mole fraction of Cu. The heat of formation decreases with the increasing mole fraction of Cu, but the HEAs AlCoCrCuxFeNi are thermodynamically stable due to their negative heats of formation.
yangfang
,
Yan Guo
,
li shaoqiang
,
Li Chengshan
,
Xiong Xiaomei
,
Wang Qingyang
,
Liu Guoqing
,
Feng Jianqing
2016, 45(4):1088-1092.
Abstract:
AlMgB14 is of great interest due to its extreme hardness, low density, high thermal stability and desirable thermoelectric properties. AlMgB14 is a very promising candidate as wear-resistant, self-lubricating and protective coatings for cutting tools and protective coatings for micro devices and micro electromechanical components. Some methods for preparing AlMgB14 super-hard materials were introduced, especially a two-step heat treatment method. AlMgB14 disks were synthesized at ambient pressure through a two-step heat treatment. In the first step, MgB2 disks doped with Al and Ti were fabricated through composition of uniformly mixed Mg, B, Al powders and different contents Ti powder in the form of pressed disks heated at 850 ℃ for 2 hours in closed argon atmosphere. And in the second step, target AlMgB14-TiB2 disks were obtained after sintering the MgB2 disks at 1050 ℃ for 0.5 hours in vacuum. The phase, microstructure and superconductivity were characterized by means of X-ray diffraction (XRD), Scanning electron microscope (SEM) and superconducting quantum interference device (SQUID). The grain size of AlMgB14 is fine and the nano-scale TiB2 particles as the second phase induced by Ti doping are uniformly distributed in the sample matrix. The research status on bulk and film of AlMgB14 and the future researching scope of AlMgB14 were introduced.
AlMgB14 is of great interest due to its extreme hardness, low density, high thermal stability and desirable thermoelectric properties. AlMgB14 is a very promising candidate as wear-resistant, self-lubricating and protective coatings for cutting tools and protective coatings for micro devices and micro electromechanical components. Some methods for preparing AlMgB14 super-hard materials were introduced, especially a two-step heat treatment method. AlMgB14 disks were synthesized at ambient pressure through a two-step heat treatment. In the first step, MgB2 disks doped with Al and Ti were fabricated through composition of uniformly mixed Mg, B, Al powders and different contents Ti powder in the form of pressed disks heated at 850 ℃ for 2 hours in closed argon atmosphere. And in the second step, target AlMgB14-TiB2 disks were obtained after sintering the MgB2 disks at 1050 ℃ for 0.5 hours in vacuum. The phase, microstructure and superconductivity were characterized by means of X-ray diffraction (XRD), Scanning electron microscope (SEM) and superconducting quantum interference device (SQUID). The grain size of AlMgB14 is fine and the nano-scale TiB2 particles as the second phase induced by Ti doping are uniformly distributed in the sample matrix. The research status on bulk and film of AlMgB14 and the future researching scope of AlMgB14 were introduced.
2010, 39(2):229-233.
Abstract:
Using the first-principles pseudopotential plane-wave methods based on the density functional theory, the elastic constants of B2-(Ni1-xFex)Al (x=0-3.0 at%) supercells with or without Ni vacancy or Ni anti-site defect were calculated in the framework of Virtual Crystal Approximation. Several parameters, such as elastic constant C44, Cauchy pressure (C12-C44), Young modulus E, the shear modulus G and their ratio G/B0, have been adopted to characterize and assess the effect of Fe alloying concentration on the ductility and hardness of NiAl intermetallic compounds. It is found that Fe addition with x < 0.6 at% is proved to be efficient to enforce the strength or hardness of NiAl intermetallic compounds either for perfect crystals or for defect crystals. No improvement of the ductility of perfect B2-NiAl crystals can be demonstrated as Fe is added in the range from 0 to 3.0 at%. The Ni vacancy or Ni anti-site defects make the intrinsic ductility of perfect B2-NiAl crystals without Fe addition to be weakened. However, an obvious decrease in the degree of the embrittlement of B2-(Ni1-xFex)Al crystals with Ni vacancies can be seen as Fe alloying concentration x is lower than 0.5 at%, and the optimum additions locate in the range from 0.2 at% to 0.4 at%. From these calculations, a deduction therefore is conduced. That is for the distinct increase in the elongation rate of a B2-NiAl single crystal with Fe addition of 0.20-0.25 at% in the experiments could originate from the correlative and cooperative effects between vacancies and Fe addition in the B2-NiAl crystal
Using the first-principles pseudopotential plane-wave methods based on the density functional theory, the elastic constants of B2-(Ni1-xFex)Al (x=0-3.0 at%) supercells with or without Ni vacancy or Ni anti-site defect were calculated in the framework of Virtual Crystal Approximation. Several parameters, such as elastic constant C44, Cauchy pressure (C12-C44), Young modulus E, the shear modulus G and their ratio G/B0, have been adopted to characterize and assess the effect of Fe alloying concentration on the ductility and hardness of NiAl intermetallic compounds. It is found that Fe addition with x < 0.6 at% is proved to be efficient to enforce the strength or hardness of NiAl intermetallic compounds either for perfect crystals or for defect crystals. No improvement of the ductility of perfect B2-NiAl crystals can be demonstrated as Fe is added in the range from 0 to 3.0 at%. The Ni vacancy or Ni anti-site defects make the intrinsic ductility of perfect B2-NiAl crystals without Fe addition to be weakened. However, an obvious decrease in the degree of the embrittlement of B2-(Ni1-xFex)Al crystals with Ni vacancies can be seen as Fe alloying concentration x is lower than 0.5 at%, and the optimum additions locate in the range from 0.2 at% to 0.4 at%. From these calculations, a deduction therefore is conduced. That is for the distinct increase in the elongation rate of a B2-NiAl single crystal with Fe addition of 0.20-0.25 at% in the experiments could originate from the correlative and cooperative effects between vacancies and Fe addition in the B2-NiAl crystal
2009, 38(3):485-487.
Abstract:
Rare earth doped phosphate luminescent nanoparticles were prepared in a Microreactor system in the ethylene glycol solution, using Ln(NO3)3·6H2O (Ln=Ce, Tb) and NaH2PO4·2H2O as raw materials. The crystal property, the shape and size of the particles of the LaPO4:Ce3+,Tb3+ nanoparticles were characterized by X-ray diffraction instrument(XRD), transmission electron microscopy(TEM). And the fluorescence property was detected by fluorescence spectrum instrument. The results indicated that the nanoparticles had hexagonal crystalline form, uniform particle size distribution and intensive fluorescence property
Rare earth doped phosphate luminescent nanoparticles were prepared in a Microreactor system in the ethylene glycol solution, using Ln(NO3)3·6H2O (Ln=Ce, Tb) and NaH2PO4·2H2O as raw materials. The crystal property, the shape and size of the particles of the LaPO4:Ce3+,Tb3+ nanoparticles were characterized by X-ray diffraction instrument(XRD), transmission electron microscopy(TEM). And the fluorescence property was detected by fluorescence spectrum instrument. The results indicated that the nanoparticles had hexagonal crystalline form, uniform particle size distribution and intensive fluorescence property
2016, 45(3):575-580.
Abstract:
The microstructure evolution of titanium alloy was decided with deformation rate in cold-deformation process, and substructure significantly influences phase transformation behavior in isothermal aging treatment. The microstructure evolution in cold-deformation and aging behavior of the TB8 alloy was investigated by X-ray diffraction (XRD), Vickers hardness (HV), field emission scanning electron microscope (FESEM) and differential scanning calorimeter (DSC). The high value of FWHM resulted from the combination of the grain distortion and dislocations, and the enhancement of the distortion and dislocations was indicated by increasing of HV value. The phase transformations of this study have reversed the effect of cold-deformation on transformation behavior of α phase precipitation in the β matrix. It suggested that there existed a possibility of a special behavior in the aging transformation of cold-deformation titanium alloy.
The microstructure evolution of titanium alloy was decided with deformation rate in cold-deformation process, and substructure significantly influences phase transformation behavior in isothermal aging treatment. The microstructure evolution in cold-deformation and aging behavior of the TB8 alloy was investigated by X-ray diffraction (XRD), Vickers hardness (HV), field emission scanning electron microscope (FESEM) and differential scanning calorimeter (DSC). The high value of FWHM resulted from the combination of the grain distortion and dislocations, and the enhancement of the distortion and dislocations was indicated by increasing of HV value. The phase transformations of this study have reversed the effect of cold-deformation on transformation behavior of α phase precipitation in the β matrix. It suggested that there existed a possibility of a special behavior in the aging transformation of cold-deformation titanium alloy.
2015, 44(5):1281-1284.
Abstract:
Experiments of vacuum annealing were carried out for nanoparticles of TiAl intermetallic compound prepared by the flow-levitation method. And the effect of annealing parameters on the phase transformation of TiAl alloy was investigated by X-ray diffraction analysis. The results show that more g-TiAl phase is transformed from a2-Ti3Al phase with the increasing of annealing temperature and time. And the grain size of two phases increases accordingly. This phase transformation is promoted after nanoparticles are compressed into a bulk by vacuum-pressing. The nanocrystalline alloy with pure g-TiAl phase is obtained after the bulk compressed from mixed phase nanoparticles is vacuum-annealed.
Experiments of vacuum annealing were carried out for nanoparticles of TiAl intermetallic compound prepared by the flow-levitation method. And the effect of annealing parameters on the phase transformation of TiAl alloy was investigated by X-ray diffraction analysis. The results show that more g-TiAl phase is transformed from a2-Ti3Al phase with the increasing of annealing temperature and time. And the grain size of two phases increases accordingly. This phase transformation is promoted after nanoparticles are compressed into a bulk by vacuum-pressing. The nanocrystalline alloy with pure g-TiAl phase is obtained after the bulk compressed from mixed phase nanoparticles is vacuum-annealed.
2016, 45(2):346-352.
Abstract:
The tensile stress-strain curves and creep curves of commercial pure titanium TA2 at service temperature range (room temperature, 353K, 423K) were observed by tensile testing and creep testing. Based on the creep testing results, the significant creep phenomenon was observed at the service temperature range, and the creep feature was changing with temperature. Then, the tensile constitutive equation and the creep constitutive equation were constructed for TA2. Combining the tensile and the creep constitutive equations, the isochronous stress-strain curves were generated. The isochronous stress-strain curves of TA2 were much lower than the tensile stress-strain curves, and the isochronous stress-strain curves are decreasing with design life. Moreover, the variation feature of isochronous stress-strain curves with design life is changing with temperature. Based on the isochronous stress-strain curves, allowable limit strain and design life, the time dependent allowable stress of CP-Ti was proposed.
The tensile stress-strain curves and creep curves of commercial pure titanium TA2 at service temperature range (room temperature, 353K, 423K) were observed by tensile testing and creep testing. Based on the creep testing results, the significant creep phenomenon was observed at the service temperature range, and the creep feature was changing with temperature. Then, the tensile constitutive equation and the creep constitutive equation were constructed for TA2. Combining the tensile and the creep constitutive equations, the isochronous stress-strain curves were generated. The isochronous stress-strain curves of TA2 were much lower than the tensile stress-strain curves, and the isochronous stress-strain curves are decreasing with design life. Moreover, the variation feature of isochronous stress-strain curves with design life is changing with temperature. Based on the isochronous stress-strain curves, allowable limit strain and design life, the time dependent allowable stress of CP-Ti was proposed.
2009, 38(2):189-192.
Abstract:
HfO2 gate dielectric films with a blocking layer of Al2O3 inserted between HfO2 layer and Si layer (HfO2/Si) were treated with rapid thermal annealing process at 700 ℃. The interfacial structure and electrical properties were reported. The results of X-ray photoelectron spectroscopy showed that the interfacial layer of SiOx transformed into SiO2 after the annealing treatment, and Hf-silicates and Hf-silicides were not detected. The results of high-resolution transmission electron microscopy indicated that the interfacial layer was composed of SiO2 for the annealed film with blocking layer. The results of the electrical measurements indicated that the equivalent oxide thickness decreased to 2.5 nm and the fixed charge density decreased to –4.5×1011/cm2 in comparison with the same thickness of HfO2 films without the blocking layer. Al2O3 layer could effectively prevent the diffusion of Si into HfO2 film and improve the interfacial and electrical performance of HfO2 film
HfO2 gate dielectric films with a blocking layer of Al2O3 inserted between HfO2 layer and Si layer (HfO2/Si) were treated with rapid thermal annealing process at 700 ℃. The interfacial structure and electrical properties were reported. The results of X-ray photoelectron spectroscopy showed that the interfacial layer of SiOx transformed into SiO2 after the annealing treatment, and Hf-silicates and Hf-silicides were not detected. The results of high-resolution transmission electron microscopy indicated that the interfacial layer was composed of SiO2 for the annealed film with blocking layer. The results of the electrical measurements indicated that the equivalent oxide thickness decreased to 2.5 nm and the fixed charge density decreased to –4.5×1011/cm2 in comparison with the same thickness of HfO2 films without the blocking layer. Al2O3 layer could effectively prevent the diffusion of Si into HfO2 film and improve the interfacial and electrical performance of HfO2 film
2009, 38(9):1514-1517.
Abstract:
The CdS/TiO2NTs nanocomposite was prepared through ion-exchange and precipitation reactions. The nanostructure properties of the composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV-visible absorption spectra (DRUVAS), fluorescence emission spectra (FES) and X-ray fluorescence analyzer (XRF). SEM results revealed that the lamellar sodium trititanate originating from the TiO2 particles individually curled to form the sodium trititanate nanotubes by self-assembled mechanism. The results of XRD, TEM and DRUVAS demonstrated that hexagonal phase CdS with about 8 nm particle size were homogeneously loaded on the surface of anatase TiO2NTs and the absorption edge of the composite was extended to the visible region. The CdS/TiO2NTs composite exhibited the highest activity of hydrogen production (1708 mL/g) by photocatalytic water decomposition in comparison with TiO2NTs and TiO2 powder under visible light irradiation (l > 400 nm) for 6 h
The CdS/TiO2NTs nanocomposite was prepared through ion-exchange and precipitation reactions. The nanostructure properties of the composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV-visible absorption spectra (DRUVAS), fluorescence emission spectra (FES) and X-ray fluorescence analyzer (XRF). SEM results revealed that the lamellar sodium trititanate originating from the TiO2 particles individually curled to form the sodium trititanate nanotubes by self-assembled mechanism. The results of XRD, TEM and DRUVAS demonstrated that hexagonal phase CdS with about 8 nm particle size were homogeneously loaded on the surface of anatase TiO2NTs and the absorption edge of the composite was extended to the visible region. The CdS/TiO2NTs composite exhibited the highest activity of hydrogen production (1708 mL/g) by photocatalytic water decomposition in comparison with TiO2NTs and TiO2 powder under visible light irradiation (l > 400 nm) for 6 h
2017, 46(7):1792-1797.
Abstract:
In the paper Laser Additive Manufacturing (LAM) has been employed to fabricate repaired samples with wrought Ti6Al4V as the substrate and Ti6Al4V (Ti64) powders with low oxygen (O≤0.13wt%) as the cladding materials. The microstructure and mechanical properties of Ti64 samples fabricated by LAM and wrought billet were investigated comparatively. The results show that the macrostructure of the laser repaired sample can be divided into three domains, including wrought substrate zone (SZ), heat affected zone (HAZ) and laser deposited zone (LDZ). The LDZ microhardness is equal to that of the SZ basically. And the HAZ microhardness is higher than both the LDZ and SZ slightly. The results of room temperature tensile test show that the strength and ductility of the wrought sample are slightly higher than the laser repaired samples. Meanwhile, the strength of the laser repaired specimen with repair ratio of 40%(i.e. area fraction of the LDZ on the transverse section of tensile sample within gauge part is 40%)is slightly lower than that of 50% repaired specimen, but the ductility is higher than the latter. Therefore it is favorable to match the strength and ductility of the wrought substrate with the LDZ with low oxygen Ti64 powders as the cladding materials, so as to improve the comprehensive properties of laser repaired Ti64 alloy. The wrought specimen tensile fracture presents a typical ductile characterization, and the repaired specimenshows a complex fractography. From the LDZ to the SZ, the tensile fracture presents a successive transformation from cleavage step to dimple fracture. It can be seen that there is a good corresponding relationship between the fracture morphology and the microstructure of the tensile samples.
In the paper Laser Additive Manufacturing (LAM) has been employed to fabricate repaired samples with wrought Ti6Al4V as the substrate and Ti6Al4V (Ti64) powders with low oxygen (O≤0.13wt%) as the cladding materials. The microstructure and mechanical properties of Ti64 samples fabricated by LAM and wrought billet were investigated comparatively. The results show that the macrostructure of the laser repaired sample can be divided into three domains, including wrought substrate zone (SZ), heat affected zone (HAZ) and laser deposited zone (LDZ). The LDZ microhardness is equal to that of the SZ basically. And the HAZ microhardness is higher than both the LDZ and SZ slightly. The results of room temperature tensile test show that the strength and ductility of the wrought sample are slightly higher than the laser repaired samples. Meanwhile, the strength of the laser repaired specimen with repair ratio of 40%(i.e. area fraction of the LDZ on the transverse section of tensile sample within gauge part is 40%)is slightly lower than that of 50% repaired specimen, but the ductility is higher than the latter. Therefore it is favorable to match the strength and ductility of the wrought substrate with the LDZ with low oxygen Ti64 powders as the cladding materials, so as to improve the comprehensive properties of laser repaired Ti64 alloy. The wrought specimen tensile fracture presents a typical ductile characterization, and the repaired specimenshows a complex fractography. From the LDZ to the SZ, the tensile fracture presents a successive transformation from cleavage step to dimple fracture. It can be seen that there is a good corresponding relationship between the fracture morphology and the microstructure of the tensile samples.
2017, 46(7):1821-1826.
Abstract:
In this research, the process of hydrodynamic deep drawing of Al2198 was investigated by using finite element simulation experimental works. And the effects of die cavity pressure, blank holder gap and pre-bulging pressure on the forming process and the thickness distribution were analyzed. The research indicated that the pressure inside the liquid chamber and the blank holder gap or blank holder force were the main factors affecting hydrodynamic deep drawing process. And appropriate pre-bulging pressure was beneficial to form a good quality parts with a relatively uniform wall thickness.
In this research, the process of hydrodynamic deep drawing of Al2198 was investigated by using finite element simulation experimental works. And the effects of die cavity pressure, blank holder gap and pre-bulging pressure on the forming process and the thickness distribution were analyzed. The research indicated that the pressure inside the liquid chamber and the blank holder gap or blank holder force were the main factors affecting hydrodynamic deep drawing process. And appropriate pre-bulging pressure was beneficial to form a good quality parts with a relatively uniform wall thickness.
2010, 39(2):224-228.
Abstract:
The creep experiment of Ti40 alloy after annealing treatment at 600 ℃ for 4 h was carried on in a temperature range from 500 ℃ to 550 ℃ with various stresses. The experimental results indicate that the creep behavior can be analyzed in two temperature intervals in this creep temperature range. The first temperature interval is ranging from 500 ℃ to 520 ℃; the second one is ranging from 535 ℃ to 550 ℃. In different temperature intervals, the alloy has different creep constitutive equations. Judging by the analysis, it is deduced that the stress has obvious effect on dislocations glide and climbing controlled by heat activation when the temperature interval was at lower temperatures (500-520 ℃). With increasing temperature, the diffusion has more and more effect on the creep deformation. In higher temperature range (535-550 ℃), the creep deformation may be determined by self-diffusion or alloying element diffusion
The creep experiment of Ti40 alloy after annealing treatment at 600 ℃ for 4 h was carried on in a temperature range from 500 ℃ to 550 ℃ with various stresses. The experimental results indicate that the creep behavior can be analyzed in two temperature intervals in this creep temperature range. The first temperature interval is ranging from 500 ℃ to 520 ℃; the second one is ranging from 535 ℃ to 550 ℃. In different temperature intervals, the alloy has different creep constitutive equations. Judging by the analysis, it is deduced that the stress has obvious effect on dislocations glide and climbing controlled by heat activation when the temperature interval was at lower temperatures (500-520 ℃). With increasing temperature, the diffusion has more and more effect on the creep deformation. In higher temperature range (535-550 ℃), the creep deformation may be determined by self-diffusion or alloying element diffusion
2015, 44(11):2907-2912.
Abstract:
High-k hafnium oxide films were deposited by atomic layer deposition (ALD) on p-type Si (100) substrates. Tetrakis-diethylamino-hafnium (TDEAH) and water were used as hafnium precursor and the oxidant, respectively. Effects of deposition parameters, e.g., flow of precursors, pressure of the reactor, and temperature of the reactor and precursors on the growth of HfO2 films were investigated. By the adjustment of deposition parameters, two growth models of HfO2 films, chemical vapour deposition (CVD) liked growth model and ALD growth model were found. Results indicate that the growth model mainly depends on Q and M. There exists a transition from CVD-liked growth model to ALD growth model by the optimization of deposition parameters. The optimal deposition parameters with a GPC (growth per cycle) of 0.1 nm /cycle were obtained. Moreover, the results show that the crystallization of HfO2 film is under the control of temperature and thickness of the film.
High-k hafnium oxide films were deposited by atomic layer deposition (ALD) on p-type Si (100) substrates. Tetrakis-diethylamino-hafnium (TDEAH) and water were used as hafnium precursor and the oxidant, respectively. Effects of deposition parameters, e.g., flow of precursors, pressure of the reactor, and temperature of the reactor and precursors on the growth of HfO2 films were investigated. By the adjustment of deposition parameters, two growth models of HfO2 films, chemical vapour deposition (CVD) liked growth model and ALD growth model were found. Results indicate that the growth model mainly depends on Q and M. There exists a transition from CVD-liked growth model to ALD growth model by the optimization of deposition parameters. The optimal deposition parameters with a GPC (growth per cycle) of 0.1 nm /cycle were obtained. Moreover, the results show that the crystallization of HfO2 film is under the control of temperature and thickness of the film.
2014, 43(2):485-489.
Abstract:
A navel technology for resistance spot welding with interventional powder thermite was proposed, which is characterized with energy saving and high efficiency. The influences of the interventional powder thermite ZnO+Al upon the nugget formation, the microstructure and the mechanical property were studied in the resistance spot welding of 2024 aluminum alloy. The results indicate that the powder thermite ZnO+Al can effectively increase the dimension of the nugget and the dentrite region with the extra help of the heat of the metallurgical reaction from the powder thermite ZnO+Al. The ZnO+Al addition increases the heterogeneous nucleation in the nugget and prompts the appearing of a large scale constituent supercooling in the solid-liquid interface front during the process of solidification, which makes the distribution of equiaxed grains more uniform and refines the dentritic bundles of the equiaxed grains in the nugget. According to the aforementioned facts, the tensile-shear strength of the nugget is improved. The experimental results show that the spot strength can increase by over 28%~200% in the range of experiments with the help of the ZnO+Al addition.
A navel technology for resistance spot welding with interventional powder thermite was proposed, which is characterized with energy saving and high efficiency. The influences of the interventional powder thermite ZnO+Al upon the nugget formation, the microstructure and the mechanical property were studied in the resistance spot welding of 2024 aluminum alloy. The results indicate that the powder thermite ZnO+Al can effectively increase the dimension of the nugget and the dentrite region with the extra help of the heat of the metallurgical reaction from the powder thermite ZnO+Al. The ZnO+Al addition increases the heterogeneous nucleation in the nugget and prompts the appearing of a large scale constituent supercooling in the solid-liquid interface front during the process of solidification, which makes the distribution of equiaxed grains more uniform and refines the dentritic bundles of the equiaxed grains in the nugget. According to the aforementioned facts, the tensile-shear strength of the nugget is improved. The experimental results show that the spot strength can increase by over 28%~200% in the range of experiments with the help of the ZnO+Al addition.
2015, 44(9):2091-2094.
Abstract:
The Sr-W type planar hexagonal ferrite was synthesized by a sol-gel method, and its morphology and phase structure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The microwave absorbing properties of the mixtures with different ratios of Ni/ferrite were studied by vector network analyzer (VAZ). The results demonstrate that with the increase of hexagonal ferrite content, the microwave absorbing peaks of the mixtures shift to higher frequencies, and when the mixture consists of 20% Ni and 80% Sr-W-type ferrite, its microwave absorbing performance is the most advantageous. When absorbing coating thickness is 2 mm, the minimum reflectivity and absorbing peak frequency is –20.69 dB at 12.08 GHz and the bandwidth less than –10 dB reaches 4 GHz. The absorbing peak shifts to low-frequency with the increase of absorbing coating thickness, and when the coating thickness reaches a certain value, the two absorbing peaks appear in the mixture in the frequency range of 2~18 GHz, which is of significance to explore the absorbing material with bandwidth effect.
The Sr-W type planar hexagonal ferrite was synthesized by a sol-gel method, and its morphology and phase structure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The microwave absorbing properties of the mixtures with different ratios of Ni/ferrite were studied by vector network analyzer (VAZ). The results demonstrate that with the increase of hexagonal ferrite content, the microwave absorbing peaks of the mixtures shift to higher frequencies, and when the mixture consists of 20% Ni and 80% Sr-W-type ferrite, its microwave absorbing performance is the most advantageous. When absorbing coating thickness is 2 mm, the minimum reflectivity and absorbing peak frequency is –20.69 dB at 12.08 GHz and the bandwidth less than –10 dB reaches 4 GHz. The absorbing peak shifts to low-frequency with the increase of absorbing coating thickness, and when the coating thickness reaches a certain value, the two absorbing peaks appear in the mixture in the frequency range of 2~18 GHz, which is of significance to explore the absorbing material with bandwidth effect.
2016, 45(4):946-951.
Abstract:
The IrO2-Ta2O5 coated titanium anodes (Ti/IrO2-Ta2O5-G) with different graphene contents were prepared by thermal decomposition method. The microstructure was analyzed by FESEM and EDX, and the electrochemical properties were investigated by electrochemical testing including cyclic voltammetry(CV), anode polarization curves, and electrochemical impedance spectroscopy(EIS). As compared with the traditional Ti/IrO2-Ta2O5 anode, the results indicate that the rugged surface morphology with tiny cracks of the Ti/IrO2-Ta2O5-G anodes offer more active center for oxygen evolution reaction and have larger electrochemically active surface area, better electrocatalytic activity for oxygen evolution. The Ti/IrO2-Ta2O5-G anode with 0.4 g稬-1 graphene contents presents the best electrochemical performance.
The IrO2-Ta2O5 coated titanium anodes (Ti/IrO2-Ta2O5-G) with different graphene contents were prepared by thermal decomposition method. The microstructure was analyzed by FESEM and EDX, and the electrochemical properties were investigated by electrochemical testing including cyclic voltammetry(CV), anode polarization curves, and electrochemical impedance spectroscopy(EIS). As compared with the traditional Ti/IrO2-Ta2O5 anode, the results indicate that the rugged surface morphology with tiny cracks of the Ti/IrO2-Ta2O5-G anodes offer more active center for oxygen evolution reaction and have larger electrochemically active surface area, better electrocatalytic activity for oxygen evolution. The Ti/IrO2-Ta2O5-G anode with 0.4 g稬-1 graphene contents presents the best electrochemical performance.
93 Effects of Sodium Tetraborate in the Electrolyte Systems on Micro-arc Oxidation of Magnesium Alloy
2016, 45(4):918-922.
Abstract:
The microstructure and corrosion resistance of ceramic coatings formed by micro-arc oxidation on magnesium alloys in electrolyte systems with different Na2B4O7 concentrations was investigated by scanning electron microscopy and electrochemical workstation respectively. The function of sodium tetraborate in the formation and growth process of micro-arc oxidation coatings was analyzed. The results showed that a compound of (B4O7) 2- and Mg2 on the anode surface was formed the water-insoluble material of Mg(BO2)2 before the occurrence of micro-arc discharge. As the concentrations of Na2B4O7 increased from 3g/L to 15g/L, the morphology of deposited layer transited from granular to net structure gradually. The formation of Mg(BO2)2 layer with a high impedance characteristic set up a suitable electric field condition for MAO process. After micro-arc discharge happened, Mg(BO2)2 on the anode surface by raising the discharge voltage enhanced the strength of single pulse discharge under constant pulse width and peak current, and then speed up the growth of micro-arc oxidation coatings.
The microstructure and corrosion resistance of ceramic coatings formed by micro-arc oxidation on magnesium alloys in electrolyte systems with different Na2B4O7 concentrations was investigated by scanning electron microscopy and electrochemical workstation respectively. The function of sodium tetraborate in the formation and growth process of micro-arc oxidation coatings was analyzed. The results showed that a compound of (B4O7) 2- and Mg2 on the anode surface was formed the water-insoluble material of Mg(BO2)2 before the occurrence of micro-arc discharge. As the concentrations of Na2B4O7 increased from 3g/L to 15g/L, the morphology of deposited layer transited from granular to net structure gradually. The formation of Mg(BO2)2 layer with a high impedance characteristic set up a suitable electric field condition for MAO process. After micro-arc discharge happened, Mg(BO2)2 on the anode surface by raising the discharge voltage enhanced the strength of single pulse discharge under constant pulse width and peak current, and then speed up the growth of micro-arc oxidation coatings.
2016, 45(8):2189-2200.
Abstract:
In this paper, the fabrication method of metal three dimensional lattice structure are classified, the characters of every method are discussed and compared. According as the characters of SPF/DB(Superplastic forming/Diffusion bonding) process, it is introduced into fabricating three dimensional lattice structure, the lattice sandwich structure is looked as three-layer or multi-layer hollow structure, three type lattice sandwich structures are fabricated, it is verified that the feasibility of SPF/DB process is validated, this new method will promote the development of metal three dimensional lattice structure.The characteristics and advantages of additive manufacturing method, plastic forming methods ,SPF/DB method are compared, it is convinced that the SPF/DB process is a suitable method to produced large size, complex shape of the sandwich structure, so in the future, lattice sandwich structure fabricated through SPF/DB process will has good prospects in hypersonic aircraft and its high thrust to weight ratio engine .
In this paper, the fabrication method of metal three dimensional lattice structure are classified, the characters of every method are discussed and compared. According as the characters of SPF/DB(Superplastic forming/Diffusion bonding) process, it is introduced into fabricating three dimensional lattice structure, the lattice sandwich structure is looked as three-layer or multi-layer hollow structure, three type lattice sandwich structures are fabricated, it is verified that the feasibility of SPF/DB process is validated, this new method will promote the development of metal three dimensional lattice structure.The characteristics and advantages of additive manufacturing method, plastic forming methods ,SPF/DB method are compared, it is convinced that the SPF/DB process is a suitable method to produced large size, complex shape of the sandwich structure, so in the future, lattice sandwich structure fabricated through SPF/DB process will has good prospects in hypersonic aircraft and its high thrust to weight ratio engine .
2016, 45(6):1437-1442.
Abstract:
Abstract:Directionally solidified Rene88DT superalloy ingots were successfully produced by electroslag remelting continuous directional solidification (ESR-CDS) technology. Compared with conventional ESR ingot, the as-cast structures of ESR-CDS Rene88DT alloy ingot were analyzed using by optical microscopy (OM)、field emission scanning electron microscopy (FESEM) with energy spectrum and transmission electron microscopy(TEM). The results showed that the ESR-CDS Rene88DT alloy ingot eliminated the region of the severe central segregation which existed commonly in the conventional ESR ingot because of the formation of intersection of interfaces between columnar crystal and equiaxed crystal or columnar crystal each other. In addition, the ESR-CDS Rene88DT alloy ingot showed smaller secondary dendritic spacing, smaller non-equilibrium precipitates phase. Due to the decreasing micro-segregation level, uniform distribution of alloy elements can be achieved when subjected to the heat treatment at 1200 oC for 24h. Statistical results of inclusions revealed that the maximum size of inclusion in the ESR-CDS Rene88DT alloy was not more than 5.89μm and the inclusion volume reduced by 60% compared with conventional ESR and P/M respectively. The hot working plasticity of directionally solidified Rene88DT superalloy can be improved, which makes a basis for implementation of cast-and-wrought (C&W) route.
Abstract:Directionally solidified Rene88DT superalloy ingots were successfully produced by electroslag remelting continuous directional solidification (ESR-CDS) technology. Compared with conventional ESR ingot, the as-cast structures of ESR-CDS Rene88DT alloy ingot were analyzed using by optical microscopy (OM)、field emission scanning electron microscopy (FESEM) with energy spectrum and transmission electron microscopy(TEM). The results showed that the ESR-CDS Rene88DT alloy ingot eliminated the region of the severe central segregation which existed commonly in the conventional ESR ingot because of the formation of intersection of interfaces between columnar crystal and equiaxed crystal or columnar crystal each other. In addition, the ESR-CDS Rene88DT alloy ingot showed smaller secondary dendritic spacing, smaller non-equilibrium precipitates phase. Due to the decreasing micro-segregation level, uniform distribution of alloy elements can be achieved when subjected to the heat treatment at 1200 oC for 24h. Statistical results of inclusions revealed that the maximum size of inclusion in the ESR-CDS Rene88DT alloy was not more than 5.89μm and the inclusion volume reduced by 60% compared with conventional ESR and P/M respectively. The hot working plasticity of directionally solidified Rene88DT superalloy can be improved, which makes a basis for implementation of cast-and-wrought (C&W) route.
2015, 44(2):509-513.
Abstract:
Based on the research and development of titanium alloys for biomedical applications in China and abroad during the past few years, the metal ions release mechanism from titanium-based alloys, and their pathogenic mechanism and protective coatings and measurements were investigated. A systematic analysis is made of the effect of the corrosion on the metal ions release mechanism from the Ti6Al4V alloy and TiNi shape memory alloy, of the relationship of metal ions with pathogenic mechanism of some diseases, and of the protective coatings and surface modification techniques inhibiting the release of the metal ions. It shows that a large number of surface modification techniques were developed in recent years to improve the biocompatibility and corrosion resistance of titanium alloys and the release of metal ions were inhibited
Based on the research and development of titanium alloys for biomedical applications in China and abroad during the past few years, the metal ions release mechanism from titanium-based alloys, and their pathogenic mechanism and protective coatings and measurements were investigated. A systematic analysis is made of the effect of the corrosion on the metal ions release mechanism from the Ti6Al4V alloy and TiNi shape memory alloy, of the relationship of metal ions with pathogenic mechanism of some diseases, and of the protective coatings and surface modification techniques inhibiting the release of the metal ions. It shows that a large number of surface modification techniques were developed in recent years to improve the biocompatibility and corrosion resistance of titanium alloys and the release of metal ions were inhibited
2015, 44(5):1169-1172.
Abstract:
The isothermal oxidation behavior of packed aluminide coatings of Ni-Cr-W superalloy at 1100 oC was investigated. Results from scanning electron microscopy and X-ray diffraction indicate that the oxidation dynamics curve of packed aluminide coatings can be divided into two stages: initial rapidly stage and metaphase slowly stage. Oxides on packed aluminide coatings surface have a transformation process as following: crystal θ-A12O3→equalaxial α-A12O3→α-A12O3→particle α-A12O3→particle unite α-A12O3 during the whole oxidation. During the initial stage of oxidation, carbides can be able to holdback coating degeneration caused by interdiffusion between Ni element and Al element.
The isothermal oxidation behavior of packed aluminide coatings of Ni-Cr-W superalloy at 1100 oC was investigated. Results from scanning electron microscopy and X-ray diffraction indicate that the oxidation dynamics curve of packed aluminide coatings can be divided into two stages: initial rapidly stage and metaphase slowly stage. Oxides on packed aluminide coatings surface have a transformation process as following: crystal θ-A12O3→equalaxial α-A12O3→α-A12O3→particle α-A12O3→particle unite α-A12O3 during the whole oxidation. During the initial stage of oxidation, carbides can be able to holdback coating degeneration caused by interdiffusion between Ni element and Al element.
2015, 44(3):775-780.
Abstract:
The refining effect of hydrogen plasma arc melting (HPAM) on refractory metals has been summarized. The structure and principle of a plasma arc melting furnace were introduced and the advantages of HPAM on refining of refractory metals were also discussed. At last H2 involved in the plasma arc melting are considered to play an important role in the melting process.
The refining effect of hydrogen plasma arc melting (HPAM) on refractory metals has been summarized. The structure and principle of a plasma arc melting furnace were introduced and the advantages of HPAM on refining of refractory metals were also discussed. At last H2 involved in the plasma arc melting are considered to play an important role in the melting process.
2014, 43(4):1013-1018.
Abstract:
Anodizing has become an important anticorrosive surface treatment technique of magnesium alloy, but the mechanism of anodic film formed on magnesium alloy is not understood fully. Several aspects were summarized up about the formation dynamics process of anodic film, including formation process, microstructure, composition, diffusion behavior of elements, the influence of alloy phase on formation of the film and the physical model. Finally, several important research problems of anodic film on Mg alloy were listed. It will benefit mastering the formation mechanism, improving the anodizing technology and enlarging the practical application.
Anodizing has become an important anticorrosive surface treatment technique of magnesium alloy, but the mechanism of anodic film formed on magnesium alloy is not understood fully. Several aspects were summarized up about the formation dynamics process of anodic film, including formation process, microstructure, composition, diffusion behavior of elements, the influence of alloy phase on formation of the film and the physical model. Finally, several important research problems of anodic film on Mg alloy were listed. It will benefit mastering the formation mechanism, improving the anodizing technology and enlarging the practical application.
