Volume 45,Issue 8,2016 Table of Contents
2016, 45(8):1917-1923.
Abstract:
Effects of Ce and Zr microalloying additions on the microstructure and tensile property of novel Al–5.8wt% Cu–1.3wt% Li alloys with an elevated Cu/Li ratio were investigated comparatively by microscopy methods and tensile tests. The microstructural observation showed that the intermetallic dispersoid was significantly refined from coarse polygonal shape to fine irregular particle with combinative addition of Ce and Zr compared to single addition of Ce or Zr. Due to the refinement and modification of intermetallic dispersoid， the fracture mode changed from brittle intergranular fracture to ductile transgranular fracture during tensile. In addition, microstructural analysis revealed that the addition of Ce promoted the precipitation of the T1 phase which was the predominant strengthen phase in Al-Cu-Li alloy. In comparison to Ce containing Al-Cu-Li alloy, Ce Zr-containing Al-Cu-Li alloy has raised the degree of supersaturation of Cu in matrix attributed to less Cu atom had been trapped in finer AlCuCe dispersoid after solution treatment. Thus it was found that the ultimate tensile strength (UTS) and yield strength (YS) increased by 19.6% and 16.1% respectively and with almost similar elongation (El), attributed to decreasing of the phase size, changing of precipitation type to T1 phase only and further grain refinement in Ce Zr-containing Al-Cu-Li alloy.
Effects of Ce and Zr microalloying additions on the microstructure and tensile property of novel Al–5.8wt% Cu–1.3wt% Li alloys with an elevated Cu/Li ratio were investigated comparatively by microscopy methods and tensile tests. The microstructural observation showed that the intermetallic dispersoid was significantly refined from coarse polygonal shape to fine irregular particle with combinative addition of Ce and Zr compared to single addition of Ce or Zr. Due to the refinement and modification of intermetallic dispersoid， the fracture mode changed from brittle intergranular fracture to ductile transgranular fracture during tensile. In addition, microstructural analysis revealed that the addition of Ce promoted the precipitation of the T1 phase which was the predominant strengthen phase in Al-Cu-Li alloy. In comparison to Ce containing Al-Cu-Li alloy, Ce Zr-containing Al-Cu-Li alloy has raised the degree of supersaturation of Cu in matrix attributed to less Cu atom had been trapped in finer AlCuCe dispersoid after solution treatment. Thus it was found that the ultimate tensile strength (UTS) and yield strength (YS) increased by 19.6% and 16.1% respectively and with almost similar elongation (El), attributed to decreasing of the phase size, changing of precipitation type to T1 phase only and further grain refinement in Ce Zr-containing Al-Cu-Li alloy.
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.
2016, 45(8):1931-1937.
Abstract:
In the present investigation, ternary Ni-W-P deposits were prepared on the mild steel (1015) substrate using electroless plating by varying sodium tungstate. Surface morphology, microstructure, and the microhardness of electroless Ni-W-P deposits were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and a MH-6 Vickers diamond indenter, respectively. The results demonstrated that the bath concentration plays a significant role in obtaining ternary Ni-W-P deposits containing various composition of phosphorus and tungsten, which decides the surface morphology and the structure. Although nodular formation is a common feature of electroless Ni-W-P deposits, composition of W decreased the P content of these deposits and hence changes the content of the nanocrystalline phase. The co-deposition of tungsten in the deposits increased the microhardness due to the solid solution strengthening of nickel induced by tungsten in the deposits and resisted regional plastic deformation. Moreover, studies on phase transformation behavior carried out by differential scanning calorimetry (DSC) showed that Ni-W-P deposits with high W content exhibited higher crystallization temperatures. Further fouling experiments indicated that the Ni-W-P deposit surfaces with different W content inhibited the adhesion of fouling compared with the mild steel surface. However, we found there is not a necessary relationship between the fouling adhesion rate and surface roughness of the ternary Ni-W-P deposits, but is intimately related to the W content.
In the present investigation, ternary Ni-W-P deposits were prepared on the mild steel (1015) substrate using electroless plating by varying sodium tungstate. Surface morphology, microstructure, and the microhardness of electroless Ni-W-P deposits were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and a MH-6 Vickers diamond indenter, respectively. The results demonstrated that the bath concentration plays a significant role in obtaining ternary Ni-W-P deposits containing various composition of phosphorus and tungsten, which decides the surface morphology and the structure. Although nodular formation is a common feature of electroless Ni-W-P deposits, composition of W decreased the P content of these deposits and hence changes the content of the nanocrystalline phase. The co-deposition of tungsten in the deposits increased the microhardness due to the solid solution strengthening of nickel induced by tungsten in the deposits and resisted regional plastic deformation. Moreover, studies on phase transformation behavior carried out by differential scanning calorimetry (DSC) showed that Ni-W-P deposits with high W content exhibited higher crystallization temperatures. Further fouling experiments indicated that the Ni-W-P deposit surfaces with different W content inhibited the adhesion of fouling compared with the mild steel surface. However, we found there is not a necessary relationship between the fouling adhesion rate and surface roughness of the ternary Ni-W-P deposits, but is intimately related to the W content.
2016, 45(8):1938-1942.
Abstract:
La1-xSmxMgNi3.6Co0.4 (x = 0-0.4) alloys were prepared by vacuum intermediate frequency induction furnace with a high purity helium gas as the protective atmosphere. The effects of partially substituting Sm for La on the phase structure, morphology and hydrogen storage properties of the alloys were investigated systematically. The detections of XRD and SEM reveal that the as-cast alloys contain two phases LaMgNi4 and LaNi5. The hydrogen storage capacity of the alloys decreases with increasing Sm content, namely 1.859, 1.707, 1.585, 1.578, 1.471 wt. %, respectively corresponding the variation of Sm content. The P-C-T curves of the alloys show flat plateaus corresponding to the absorption/desorption pressure plateaus of the LaMgNi4 hydride. Meanwhile, the enthalpy change (ΔH) and entropy change (ΔS) of the LaMgNi4 hydrides for hydriding decrease from -40.37 kJ/mol (x = 0) to -26.99 kJ/mol (x = 0.4) and from -101.9 J/mol/K (x = 0) to -77.56 J/mol/K (x = 0.4), respectively. The electrochemical measurement displays that the maximum discharge capacity of the alloy electrodes declines from 347 mAh/g to 270.5 mAh/g, to be very similar with the trend of the gaseous hydrogen absorption capacity. On the contrary, the cycle stability of the as-cast alloys obviously augments with the Sm content increasing, which can be attributed to the facilitated corrosion resistance by Sm substituting.
La1-xSmxMgNi3.6Co0.4 (x = 0-0.4) alloys were prepared by vacuum intermediate frequency induction furnace with a high purity helium gas as the protective atmosphere. The effects of partially substituting Sm for La on the phase structure, morphology and hydrogen storage properties of the alloys were investigated systematically. The detections of XRD and SEM reveal that the as-cast alloys contain two phases LaMgNi4 and LaNi5. The hydrogen storage capacity of the alloys decreases with increasing Sm content, namely 1.859, 1.707, 1.585, 1.578, 1.471 wt. %, respectively corresponding the variation of Sm content. The P-C-T curves of the alloys show flat plateaus corresponding to the absorption/desorption pressure plateaus of the LaMgNi4 hydride. Meanwhile, the enthalpy change (ΔH) and entropy change (ΔS) of the LaMgNi4 hydrides for hydriding decrease from -40.37 kJ/mol (x = 0) to -26.99 kJ/mol (x = 0.4) and from -101.9 J/mol/K (x = 0) to -77.56 J/mol/K (x = 0.4), respectively. The electrochemical measurement displays that the maximum discharge capacity of the alloy electrodes declines from 347 mAh/g to 270.5 mAh/g, to be very similar with the trend of the gaseous hydrogen absorption capacity. On the contrary, the cycle stability of the as-cast alloys obviously augments with the Sm content increasing, which can be attributed to the facilitated corrosion resistance by Sm substituting.
2016, 45(8):1943-1948.
Abstract:
The film-induced stress and susceptibility to stress corrosion cracking (SCC) of 7050 aluminum alloy in the chloride solution at various potentials have been studied in this paper. The results showed that a large tensile stress was generated by the passive film during original corrosion. The passive film induced tensile stress increased obviously with an increase in potential under an anodic potential; however, it decreased with an increase in potential when the potential E≥-1100 mVSCE while it increased when E＜-1100 mVSCE under a cathodic potential. The variation of film-induced stress with potential was consistent with that of the susceptibility to SCC with potential.
The film-induced stress and susceptibility to stress corrosion cracking (SCC) of 7050 aluminum alloy in the chloride solution at various potentials have been studied in this paper. The results showed that a large tensile stress was generated by the passive film during original corrosion. The passive film induced tensile stress increased obviously with an increase in potential under an anodic potential; however, it decreased with an increase in potential when the potential E≥-1100 mVSCE while it increased when E＜-1100 mVSCE under a cathodic potential. The variation of film-induced stress with potential was consistent with that of the susceptibility to SCC with potential.
2016, 45(8):1949-1955.
Abstract:
In order to obtain extremely rapid solidification structure far from equilibrium, the surface of AZ31B magnesium alloy was melted by CO2 laser, while the samples were extremely rapidly cooled in liquid nitrogen. Microstructure, performance and strengthening mechanism of laser melted layer were investigated. The results showed that grains of melted layer were highly refined and grain size was nearly uniform. The melted layer contained α-Mg and β-Mg17Al12, but β-Mg17Al12 which distributed along grain boundary was few. Because of strengthening mechanisms of fined grains, super solid solution and dislocation, microhardness of melted layer was up to 140HV. Wear loss of melted sample cooled in liquid nitrogen was about 50% less than that of the untreated sample and melted sample cooled in air, and wear resistance of melted layer was improved obviously. Impacting fracture morphology indicated that there was trace of plastic deformation, thus, plasticity and ductility were also improved.
In order to obtain extremely rapid solidification structure far from equilibrium, the surface of AZ31B magnesium alloy was melted by CO2 laser, while the samples were extremely rapidly cooled in liquid nitrogen. Microstructure, performance and strengthening mechanism of laser melted layer were investigated. The results showed that grains of melted layer were highly refined and grain size was nearly uniform. The melted layer contained α-Mg and β-Mg17Al12, but β-Mg17Al12 which distributed along grain boundary was few. Because of strengthening mechanisms of fined grains, super solid solution and dislocation, microhardness of melted layer was up to 140HV. Wear loss of melted sample cooled in liquid nitrogen was about 50% less than that of the untreated sample and melted sample cooled in air, and wear resistance of melted layer was improved obviously. Impacting fracture morphology indicated that there was trace of plastic deformation, thus, plasticity and ductility were also improved.
2016, 45(8):1956-1960.
Abstract:
Electrochemical behavior of Ce(III) and underpotential deposition of Al-Ce alloys were investigated at an Al active electrode in LiCl-KCl-CeCl3 melts. Compared with the cyclic voltammetry curves on a Mo electrode, the redox potential of Ce(III)/Ce at an Al electrode was more positive; there were two new plateaus between the deposition plateau of Al and Ce metal by circuit chronopotentiometry, which means forming two kinds of intermetallic compound. These results showed Ce(III) forming intermetallic compound due to underpotential deposition by electrochemical theory. Furthermore, these were confirmed by Al-Ce alloys, which were obtained at Al active electrode in LiCl-KCl-CeCl3 melts after potentiostatic deposition under the same condition. The formation of AlCe and AlCe3 were illuminated by X-ray diffraction (XRD). The analysis of scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) showed that cerium exists at the surface of Al electrode to form a layer, which was about 28?m evenly coated the Al electrode.
Electrochemical behavior of Ce(III) and underpotential deposition of Al-Ce alloys were investigated at an Al active electrode in LiCl-KCl-CeCl3 melts. Compared with the cyclic voltammetry curves on a Mo electrode, the redox potential of Ce(III)/Ce at an Al electrode was more positive; there were two new plateaus between the deposition plateau of Al and Ce metal by circuit chronopotentiometry, which means forming two kinds of intermetallic compound. These results showed Ce(III) forming intermetallic compound due to underpotential deposition by electrochemical theory. Furthermore, these were confirmed by Al-Ce alloys, which were obtained at Al active electrode in LiCl-KCl-CeCl3 melts after potentiostatic deposition under the same condition. The formation of AlCe and AlCe3 were illuminated by X-ray diffraction (XRD). The analysis of scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) showed that cerium exists at the surface of Al electrode to form a layer, which was about 28?m evenly coated the Al electrode.
2016, 45(8):1961-1966.
Abstract:
In this work, Cu/Ag/Graphite coating was deposited on steel substrates by plasma spraying process. The tribological behavior of Cu/Ag/Graphite coating under different currents has been tested using a HST-100 pin-on-disc friction and wear tester in an air atmosphere with humidity of about 50%. The coating microstructure, phase composition,worn surface and debris were characterized by field emission scanning electron microscope (FESEM), energy dispersive X-ray spectrum (EDS) and X-ray diffraction (XRD). The results show that Cu/Ag alloy forms a continuous metal network in as-received coating and the deposited graphite particle demonstrates an obvious orientation direction parallel to the substrate. With the increasing current from 0A to 50A, it was found that the wear rate of Cu/Ag/Graphite coating is increased and related closely with the pin contact pressure and sliding velocity. It is of interesting to note that the friction coefficient of Cu/Ag/Graphite coating was not affected by the increasing currents under the same contact pressure and velocity in this work. Graphite transfer film and oxidization layer were the main reasons for stable electrical sliding process. Under no current applied, the wear mechanism was abrasive wear; however, the electrical wear would become the main wear mechanism with the increase of current intensity during electrical sliding process.
In this work, Cu/Ag/Graphite coating was deposited on steel substrates by plasma spraying process. The tribological behavior of Cu/Ag/Graphite coating under different currents has been tested using a HST-100 pin-on-disc friction and wear tester in an air atmosphere with humidity of about 50%. The coating microstructure, phase composition,worn surface and debris were characterized by field emission scanning electron microscope (FESEM), energy dispersive X-ray spectrum (EDS) and X-ray diffraction (XRD). The results show that Cu/Ag alloy forms a continuous metal network in as-received coating and the deposited graphite particle demonstrates an obvious orientation direction parallel to the substrate. With the increasing current from 0A to 50A, it was found that the wear rate of Cu/Ag/Graphite coating is increased and related closely with the pin contact pressure and sliding velocity. It is of interesting to note that the friction coefficient of Cu/Ag/Graphite coating was not affected by the increasing currents under the same contact pressure and velocity in this work. Graphite transfer film and oxidization layer were the main reasons for stable electrical sliding process. Under no current applied, the wear mechanism was abrasive wear; however, the electrical wear would become the main wear mechanism with the increase of current intensity during electrical sliding process.
2016, 45(8):1967-1972.
Abstract:
In this paper, microstructure evolution of extruded Mg-2Zn-0.5Y alloy in semisolid isothermal heat treatment process was investigated. The results show that in the alloy there are α-Mg, I-Phase and W-phase, and the average grain size of α-Mg is 7 μm. During isothermal heat treatment at 793K, the grain continued growing and no liquid phase appeared until isothermal holding time arrived at 4min. With isothermal temperature raising and holding time increasing, solid α-Mg grains in the alloy were gradually growing and separated by liquid phases. Meanwhile, the liquid phase locating both at the grain boundaries and in the grain interior significantly increased. It is also found that at higher solid fractions, particle coarsening mechanism and solid particle remelting mechanism both play major roles. While at lower solid fractions, Ostwald ripening is the major mechanism and coalescence of adjacent particles could still be observed.
In this paper, microstructure evolution of extruded Mg-2Zn-0.5Y alloy in semisolid isothermal heat treatment process was investigated. The results show that in the alloy there are α-Mg, I-Phase and W-phase, and the average grain size of α-Mg is 7 μm. During isothermal heat treatment at 793K, the grain continued growing and no liquid phase appeared until isothermal holding time arrived at 4min. With isothermal temperature raising and holding time increasing, solid α-Mg grains in the alloy were gradually growing and separated by liquid phases. Meanwhile, the liquid phase locating both at the grain boundaries and in the grain interior significantly increased. It is also found that at higher solid fractions, particle coarsening mechanism and solid particle remelting mechanism both play major roles. While at lower solid fractions, Ostwald ripening is the major mechanism and coalescence of adjacent particles could still be observed.
2016, 45(8):1973-1977.
Abstract:
Employing the first-principles simulation combined with the statistical model, we have investigated the interplay between impurity of nitrogen (N) and vacancy in molybdenum (Mo). Single N atom is energetically favorable occupying the octahedral interstitial site. N atom can be found to easily bond at vacancy, and the trapping energy of N trapped by vacancy is 2.71 eV, in good agreement with the experimental result. Further, we predict vacancy concentration in the form of N1V complex in Mo, which notablely increases due to the presence of N, despite the concentration of interstitial N is still higher than that of N1V complexes. The results demonstrate the key role of vacancy on N trapping in Mo.
Employing the first-principles simulation combined with the statistical model, we have investigated the interplay between impurity of nitrogen (N) and vacancy in molybdenum (Mo). Single N atom is energetically favorable occupying the octahedral interstitial site. N atom can be found to easily bond at vacancy, and the trapping energy of N trapped by vacancy is 2.71 eV, in good agreement with the experimental result. Further, we predict vacancy concentration in the form of N1V complex in Mo, which notablely increases due to the presence of N, despite the concentration of interstitial N is still higher than that of N1V complexes. The results demonstrate the key role of vacancy on N trapping in Mo.
2016, 45(8):1978-1982.
Abstract:
To improve the mechanical properties of AZ91D alloy, squeeze casting process was employed to fabricate AZ91D magnesium matrix composites reinforced with stable icosahedral quasicrystal particles which were introduced as Mg-Zn-Y quasicrystal master alloy. The effects of quasicrystal master alloy content on microstructure and mechanical properties of composites were investigated. The results show that squeeze casting process is an effective method to refine grain size. The composites comprise α-Mg matrix, β-Mg17Al12 phases that disperse on grain boundaries and Mg3Zn6Y quasicrystal particles. A stable interface between the quasicrystal particles and the Mg matrix is observed. The composite exhibits the maximum ultimate tensile strength of 194.3 MPa and the maximum elongation of 9.2% respectively when the mass fraction of quasicrystal master alloy is 5%. The reinforcement mechanism is concluded as fine-grain strengthening and quasicrystal particle strengthening.
To improve the mechanical properties of AZ91D alloy, squeeze casting process was employed to fabricate AZ91D magnesium matrix composites reinforced with stable icosahedral quasicrystal particles which were introduced as Mg-Zn-Y quasicrystal master alloy. The effects of quasicrystal master alloy content on microstructure and mechanical properties of composites were investigated. The results show that squeeze casting process is an effective method to refine grain size. The composites comprise α-Mg matrix, β-Mg17Al12 phases that disperse on grain boundaries and Mg3Zn6Y quasicrystal particles. A stable interface between the quasicrystal particles and the Mg matrix is observed. The composite exhibits the maximum ultimate tensile strength of 194.3 MPa and the maximum elongation of 9.2% respectively when the mass fraction of quasicrystal master alloy is 5%. The reinforcement mechanism is concluded as fine-grain strengthening and quasicrystal particle strengthening.
luo laima
,
tanxiaoyue
,
DING Xiao-yu
,
LU ZELONG
,
LUO Guang-nan
,
ZANXIANG
,
ZHU Xiao-yong
,
WU Yu-cheng
2016, 45(8):1983-1987.
Abstract:
The W/Cu graded heat-sink materials with high density were fabricated by electroless plating and powder metallurgy. The microstructure, interface and fracture of the graded heat-sink materials were observed using the field emission scanning electron microscope (FESEM). The mechanical properties of the materials such as bending strength and hardness were determined. The experimental results showed that the structure of each layer was uniform and dense. The components of the cross-section presented a graded distribution. There was no obvious interface among layers. The relative density of three-layer W/Cu graded heat-sink materials reached 99.2%. The average values of microhardness of radiating layer, transitional layer and sealing layer were HV200, 210 and 240, respectively. It is indicated through the experimental results of bending strength that the bending strengths of the sealing layer and the radiating layer as the load-bearing surfaces were 428.5 MPa and 480.7MPa, respectively.
The W/Cu graded heat-sink materials with high density were fabricated by electroless plating and powder metallurgy. The microstructure, interface and fracture of the graded heat-sink materials were observed using the field emission scanning electron microscope (FESEM). The mechanical properties of the materials such as bending strength and hardness were determined. The experimental results showed that the structure of each layer was uniform and dense. The components of the cross-section presented a graded distribution. There was no obvious interface among layers. The relative density of three-layer W/Cu graded heat-sink materials reached 99.2%. The average values of microhardness of radiating layer, transitional layer and sealing layer were HV200, 210 and 240, respectively. It is indicated through the experimental results of bending strength that the bending strengths of the sealing layer and the radiating layer as the load-bearing surfaces were 428.5 MPa and 480.7MPa, respectively.
2016, 45(8):1988-1991.
Abstract:
CeO2 is a promising material for the utilization of solar light in photocatalytic reactions. However, the major obstacle for the studies is the lack of reliable methods to incorporate the desired elements such as nitrogen into the crystal lattice of CeO2. In this study, nitrogen-doped CeO2 thin film was synthesized by IBAD technique. With this technique, the nitrogen can be heavily and uniformly doped in CeO2 thin films. XPS analysis results clearly demonstrated the greatest N contraction of 25 mol% can be achieved in CeO2 thin films which was much higher than that via traditional methods. The high resolution N 1s spectrum shows that nitrogen dopants were uniformly doped into CeO2 lattice by substituting O via IBAD. The XRD results indicated ion bombardment on the growing film surface did not alter the crystal structure of the film by itself. Instead, the heavy nitrogen doping can induce smaller grain size of CeO2. The SEM images showed that with the increase of N doping, the surface became smoother with smaller particle size. The heavily nitrogen doping can also induce a red shift of the visible light absorbance from 380 to 450 nm.
CeO2 is a promising material for the utilization of solar light in photocatalytic reactions. However, the major obstacle for the studies is the lack of reliable methods to incorporate the desired elements such as nitrogen into the crystal lattice of CeO2. In this study, nitrogen-doped CeO2 thin film was synthesized by IBAD technique. With this technique, the nitrogen can be heavily and uniformly doped in CeO2 thin films. XPS analysis results clearly demonstrated the greatest N contraction of 25 mol% can be achieved in CeO2 thin films which was much higher than that via traditional methods. The high resolution N 1s spectrum shows that nitrogen dopants were uniformly doped into CeO2 lattice by substituting O via IBAD. The XRD results indicated ion bombardment on the growing film surface did not alter the crystal structure of the film by itself. Instead, the heavy nitrogen doping can induce smaller grain size of CeO2. The SEM images showed that with the increase of N doping, the surface became smoother with smaller particle size. The heavily nitrogen doping can also induce a red shift of the visible light absorbance from 380 to 450 nm.
2016, 45(8):1992-1996.
Abstract:
Thin films of amorphous indium gallium zinc oxide (a-IGZO) were fabricated by DC magnetron sputtering. The influence of sputtering pressure on the microstructures and the electronic properties were investigated in details. AFM characterization on surface morphology demonstrated that the surface roughness increases with the sputtering pressure. The oxygen vacancies of the a-IGZO films changes considerably and were reduced significantly with increasing sputtering pressure, as disclosed by X-ray photoelectron spectroscopy. Both the increased surface roughness and reduced oxygen vacancy are detrimental to the performance of a-IGZO TFTs. From this point of view, the sputtering should be done at a proper pressure of 0.06 Pa in order to ensure the enhanced performance. Specifically, the electron saturation mobility (μsat) and the threshold voltage (VTH) of the a-IGZO TFTs are 3.32 cm2/(V?s) and 24.6V at such a sputtering condition.
Thin films of amorphous indium gallium zinc oxide (a-IGZO) were fabricated by DC magnetron sputtering. The influence of sputtering pressure on the microstructures and the electronic properties were investigated in details. AFM characterization on surface morphology demonstrated that the surface roughness increases with the sputtering pressure. The oxygen vacancies of the a-IGZO films changes considerably and were reduced significantly with increasing sputtering pressure, as disclosed by X-ray photoelectron spectroscopy. Both the increased surface roughness and reduced oxygen vacancy are detrimental to the performance of a-IGZO TFTs. From this point of view, the sputtering should be done at a proper pressure of 0.06 Pa in order to ensure the enhanced performance. Specifically, the electron saturation mobility (μsat) and the threshold voltage (VTH) of the a-IGZO TFTs are 3.32 cm2/(V?s) and 24.6V at such a sputtering condition.
2016, 45(8):1997-2002.
Abstract:
In this paper, the Cu-8wt%Ag alloy was prepared by two kinds of preparation technologies, namely the continuous casting cold wire-drawing deformation preparation technology (CC CD) and the continuous casting equal channel angular pressing cold wire-drawing deformation preparation technology (CC ECAP CD), and subsequently was performed the aging treatment. This paper measured respectively the mechanical property and the electrical property of the Cu-8wt%Ag alloy with the different strain, explored the changing rules of the microstructure, the mechanical property and the electrical property by the different preparation technologies, analyzed the changing reasons of performance and discussed whether the better comprehensive performance was acquired by combining the ECAP with the traditional cold-processing. The results show that the comprehensive performance of the Cu-8wt%Ag alloy prepared by CC ECAP CD is a little better than that by CC CD. It is significant and valuable to solve the waxing and waning problem between the high strength and high conductivity of the Cu-Ag alloy.
In this paper, the Cu-8wt%Ag alloy was prepared by two kinds of preparation technologies, namely the continuous casting cold wire-drawing deformation preparation technology (CC CD) and the continuous casting equal channel angular pressing cold wire-drawing deformation preparation technology (CC ECAP CD), and subsequently was performed the aging treatment. This paper measured respectively the mechanical property and the electrical property of the Cu-8wt%Ag alloy with the different strain, explored the changing rules of the microstructure, the mechanical property and the electrical property by the different preparation technologies, analyzed the changing reasons of performance and discussed whether the better comprehensive performance was acquired by combining the ECAP with the traditional cold-processing. The results show that the comprehensive performance of the Cu-8wt%Ag alloy prepared by CC ECAP CD is a little better than that by CC CD. It is significant and valuable to solve the waxing and waning problem between the high strength and high conductivity of the Cu-Ag alloy.
2016, 45(8):2133-2138.
Abstract:
The effect of B addition on the morphology of iron-rich phase in Al-Si alloy with ?1.0% Fe and ?1.0% Mn was invesitigated with optical microscopy, SEM, EDS and DSC. The obtained results show that an appropriate amount of B addition results in not only an obvious refinement on Al-Si alloy grain, but also the morphology, size and volume fraction of the iron-rich phases. With 3% Al-3B addition, the volume fraction and mean size of the iron-rich phases were reduced to 4.13% and 7.5 μm, respectively. With the increase of Al-3B addition within 3%, the formation of coarse primary iron-rich phase has been suppressed, and the primary coarse iron phase, large size dendritic iron-rich phase and netlike iron-rich phase are transformed into small size and high density of dendritic, chinese script shaped and granular. However, excessive Al-3B addition leads to the formation of polygon primary iron rich phase and refined grain size and iron-rich phase.
The effect of B addition on the morphology of iron-rich phase in Al-Si alloy with ?1.0% Fe and ?1.0% Mn was invesitigated with optical microscopy, SEM, EDS and DSC. The obtained results show that an appropriate amount of B addition results in not only an obvious refinement on Al-Si alloy grain, but also the morphology, size and volume fraction of the iron-rich phases. With 3% Al-3B addition, the volume fraction and mean size of the iron-rich phases were reduced to 4.13% and 7.5 μm, respectively. With the increase of Al-3B addition within 3%, the formation of coarse primary iron-rich phase has been suppressed, and the primary coarse iron phase, large size dendritic iron-rich phase and netlike iron-rich phase are transformed into small size and high density of dendritic, chinese script shaped and granular. However, excessive Al-3B addition leads to the formation of polygon primary iron rich phase and refined grain size and iron-rich phase.
2016, 45(8):2003-2008.
Abstract:
The microstructure and electrical conductivity of A2Zr2O7 ceramic have been investigated by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) coupled with selected area electron diffraction (SAED), Raman spectroscopy and Impedance spectroscopy. The results show that the degree of structural order of rare-earth zirconates A2Zr2O7 ceramics gradually decreases with decreasing ionic radius of rare-earth cations. The Sm2Zr2O7 and Eu2Zr2O7 ceramics exhibit an ordered pyrochlore phase, while Gd2Zr2O7 and Dy2Zr2O7 ceramics have a disordered fluorite phase. Pyrochlore-type Eu2Zr2O7 ceramic with a relatively low structural order degree shows the maximum grain conductivity of 1.03?10–2S?cm–1 at 1173K, as compared with that of the other rare-earth zirconates.
The microstructure and electrical conductivity of A2Zr2O7 ceramic have been investigated by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) coupled with selected area electron diffraction (SAED), Raman spectroscopy and Impedance spectroscopy. The results show that the degree of structural order of rare-earth zirconates A2Zr2O7 ceramics gradually decreases with decreasing ionic radius of rare-earth cations. The Sm2Zr2O7 and Eu2Zr2O7 ceramics exhibit an ordered pyrochlore phase, while Gd2Zr2O7 and Dy2Zr2O7 ceramics have a disordered fluorite phase. Pyrochlore-type Eu2Zr2O7 ceramic with a relatively low structural order degree shows the maximum grain conductivity of 1.03?10–2S?cm–1 at 1173K, as compared with that of the other rare-earth zirconates.
2016, 45(8):2009-2015.
Abstract:
Titanium have been widely used in aerospace and other fields . But one of the key factors leading to low processing efficiency is the sticking problem between titanium plate and the roll surface during the process of cold rolling. Focusing on this problem, the interfacial adhesion energies between Ti, Al, Cu, Mg and Fe and their internal binding energies were calculated. It is found that the interfacial adhesion energy between Ti and Fe is not only greater than the internal binding energy of Ti, but also greater than the internal binding energy of Fe, which is different from the other three metals. Therefore, fracture will occur on the deeper layer of Titanium plate’s substrate with close contact and relative movement between Fe and Ti surfaces. Then, the sticking situation of TA2 cold-rolling is analyzed. It is found that lubricating film is easier to rupture than other metals due to titanium’s unique properties,, which results in direct contact and sticking between roller and Titanium plate. Consequently, the sticking index is proposed to characterize the degree of sticking, the impact of draft rolling schedule, rolling speed, lubricant type on the degree of sticking is analyzed. It is concluded that the cold-rolling speed of TA2 should be lower than 3m/s, the reduction rate of each pass should be less than 20%, which is important to guide the productive practice and prevent sticking.
Titanium have been widely used in aerospace and other fields . But one of the key factors leading to low processing efficiency is the sticking problem between titanium plate and the roll surface during the process of cold rolling. Focusing on this problem, the interfacial adhesion energies between Ti, Al, Cu, Mg and Fe and their internal binding energies were calculated. It is found that the interfacial adhesion energy between Ti and Fe is not only greater than the internal binding energy of Ti, but also greater than the internal binding energy of Fe, which is different from the other three metals. Therefore, fracture will occur on the deeper layer of Titanium plate’s substrate with close contact and relative movement between Fe and Ti surfaces. Then, the sticking situation of TA2 cold-rolling is analyzed. It is found that lubricating film is easier to rupture than other metals due to titanium’s unique properties,, which results in direct contact and sticking between roller and Titanium plate. Consequently, the sticking index is proposed to characterize the degree of sticking, the impact of draft rolling schedule, rolling speed, lubricant type on the degree of sticking is analyzed. It is concluded that the cold-rolling speed of TA2 should be lower than 3m/s, the reduction rate of each pass should be less than 20%, which is important to guide the productive practice and prevent sticking.
2016, 45(8):2016-2019.
Abstract:
Cu-Gd2O3 composites were prepared by the spark plasma sintering apparatus, and the research was mainly focused on physical properties and the interface reaction layer in the composites. The Gd2O3 powder distributed in the composite dispersively, and with the increase of the amount of Gd2O3 a three-dimensional grid structure formed in the matrix. New phase Gd2CuO4 was detected by XRD analysis, and the interface reaction between Gd2O3 and Cu matrix during sintering process was observed by TEM. The thickness of reaction layer and transition zone became broaden with the increase of the temperature. It was an effectively way to improve the mechanical properties of materials by the control of the thickness of reaction layer.
Cu-Gd2O3 composites were prepared by the spark plasma sintering apparatus, and the research was mainly focused on physical properties and the interface reaction layer in the composites. The Gd2O3 powder distributed in the composite dispersively, and with the increase of the amount of Gd2O3 a three-dimensional grid structure formed in the matrix. New phase Gd2CuO4 was detected by XRD analysis, and the interface reaction between Gd2O3 and Cu matrix during sintering process was observed by TEM. The thickness of reaction layer and transition zone became broaden with the increase of the temperature. It was an effectively way to improve the mechanical properties of materials by the control of the thickness of reaction layer.
2016, 45(8):2020-2025.
Abstract:
Micro/nano multi-level structure tantalum coating was prepared on medical titanium substrate surface using plasma spraying technique. The surface morphology, chemical composition and phase composition were analyzed by SEM, EDS and XRD, and the adhesion between substrate and coating was investigated by tensile method. The surface adsorption amount of protein of micro/nano multi-level tantalum coating and titanium substrate was compared by using BSA. The result showed that when the titanium-based tantalum coating was prepared under the spray distance was 110 mm and spray power was 30 kW, typical multi-level structural features can be seen, combined with good binding force and high Ta phase content; protein adsorption test showed that titanium-based tantalum coatings have good protein adsorption capacity, whose adsorption amount were higher than control samples.
Micro/nano multi-level structure tantalum coating was prepared on medical titanium substrate surface using plasma spraying technique. The surface morphology, chemical composition and phase composition were analyzed by SEM, EDS and XRD, and the adhesion between substrate and coating was investigated by tensile method. The surface adsorption amount of protein of micro/nano multi-level tantalum coating and titanium substrate was compared by using BSA. The result showed that when the titanium-based tantalum coating was prepared under the spray distance was 110 mm and spray power was 30 kW, typical multi-level structural features can be seen, combined with good binding force and high Ta phase content; protein adsorption test showed that titanium-based tantalum coatings have good protein adsorption capacity, whose adsorption amount were higher than control samples.
2016, 45(8):2026-2030.
Abstract:
High-temperature oxidation resistance in static air of 0Cr18Ni9Ti stainless steel (substrate for short), and the substrates after treated respectively by hafnizing process, hafnizing carburizing process were investigated. The results show that: Thickness of Hf-alloyed layer is 35 um, the layer found continuous and dense with no holes, combined with the matrix as a metallurgical bond, the surface phase is Hf2Fe, HfC, Hf; Thickness of Hf C layer is 100 um, and dispersively distributed many granular and short rod carbide particles which size 1 ~ 2um, the main types are MC, M7C3, M23C6. The oxidation rate of Hf-alloyed sample in 1050℃ and 1100℃ are just 1/3, 1/8 that of substrate, and Hf C layer sample about 1/8, 1/25, the oxidation rate increases as the temperature rises, the rate and oxidation mass is Hf C layer sample < Hf-alloyed sample < substrate, and the oxidation mass comply with the parabolic law; The surface alloying elements reduced, Hf increased after hafnizing and carburizing successively, and surface flaking improved, oxidation defects reduced and holes turn smaller, Hf can solidify the surface oxide layer and improve solid solution strengthening, carbide particles as HfC and oxides as HfO2 can reduce the rate of diffusion of oxygen ions, improved oxidation resistance significantly.
High-temperature oxidation resistance in static air of 0Cr18Ni9Ti stainless steel (substrate for short), and the substrates after treated respectively by hafnizing process, hafnizing carburizing process were investigated. The results show that: Thickness of Hf-alloyed layer is 35 um, the layer found continuous and dense with no holes, combined with the matrix as a metallurgical bond, the surface phase is Hf2Fe, HfC, Hf; Thickness of Hf C layer is 100 um, and dispersively distributed many granular and short rod carbide particles which size 1 ~ 2um, the main types are MC, M7C3, M23C6. The oxidation rate of Hf-alloyed sample in 1050℃ and 1100℃ are just 1/3, 1/8 that of substrate, and Hf C layer sample about 1/8, 1/25, the oxidation rate increases as the temperature rises, the rate and oxidation mass is Hf C layer sample < Hf-alloyed sample < substrate, and the oxidation mass comply with the parabolic law; The surface alloying elements reduced, Hf increased after hafnizing and carburizing successively, and surface flaking improved, oxidation defects reduced and holes turn smaller, Hf can solidify the surface oxide layer and improve solid solution strengthening, carbide particles as HfC and oxides as HfO2 can reduce the rate of diffusion of oxygen ions, improved oxidation resistance significantly.
2016, 45(8):2031-2035.
Abstract:
In this paper, the hydrogenation-desorption technology was applied to process as-cast ZK60 alloy, and the nanocrystallization mechanism in this processing was studied. The phase and microstructure evolution of ZK60 alloy powders at different states (before hydrogenation, after hydrogenation and after desorption) were characterized by powder X-ray diffraction, optical microscopy and transmission electron microscopy, respectively. The results reveal that ZK60 powders are completely hydrogenated at 450 ℃ under 2 MPa for 12 h and then thoroughly dehydrogenated at 350 ℃ for 3 h in vacuum; meanwhile, the grain sizes of ZK60 alloy powders are refined from 150 μm to 30 nm as well.
In this paper, the hydrogenation-desorption technology was applied to process as-cast ZK60 alloy, and the nanocrystallization mechanism in this processing was studied. The phase and microstructure evolution of ZK60 alloy powders at different states (before hydrogenation, after hydrogenation and after desorption) were characterized by powder X-ray diffraction, optical microscopy and transmission electron microscopy, respectively. The results reveal that ZK60 powders are completely hydrogenated at 450 ℃ under 2 MPa for 12 h and then thoroughly dehydrogenated at 350 ℃ for 3 h in vacuum; meanwhile, the grain sizes of ZK60 alloy powders are refined from 150 μm to 30 nm as well.
2016, 45(8):2036-2040.
Abstract:
In order to improve the tribological properties of sea frictional key components, uniform and gradient CrCN coating were deposited on 316L stainless steel and single crystal silicon by multi arc ion plating technique. The microstructures, mechanical performance, corrosion resistance and tribological properties in seawater were systematically investigated by XRD, XPS, SEM, Scratch test system, nano-indentation, 273A electrochemical workstation and ball-on-disc tribol-meter. The results showed that the grain size, crystallinity of Cr7C3(421), mechanical performance and corrosion resistance of gradient CrCN coating were better than uniform CrCN coating. Friction coefficient and wear ratio in seawater of gradient CrCN coating were lower than uniform CrCN coating, which indicates the gradient CrCN coating has a good tribological properties than uniform CrCN coating.
In order to improve the tribological properties of sea frictional key components, uniform and gradient CrCN coating were deposited on 316L stainless steel and single crystal silicon by multi arc ion plating technique. The microstructures, mechanical performance, corrosion resistance and tribological properties in seawater were systematically investigated by XRD, XPS, SEM, Scratch test system, nano-indentation, 273A electrochemical workstation and ball-on-disc tribol-meter. The results showed that the grain size, crystallinity of Cr7C3(421), mechanical performance and corrosion resistance of gradient CrCN coating were better than uniform CrCN coating. Friction coefficient and wear ratio in seawater of gradient CrCN coating were lower than uniform CrCN coating, which indicates the gradient CrCN coating has a good tribological properties than uniform CrCN coating.
2016, 45(8):2041-2045.
Abstract:
The lattice parameters, formation energy, elastic modulus and differential charge density of NiTi alloyed by transition elements have been calculated by using the first principle method based on density functional theory (DFT). Then we can discuss the site preference of transition elements in NiTi and the influence of them on the martensitic transformation temperature of NiTi. The results show that, when added to NiTi Alloy: (1) the groups of V, Cr, Mn, Fe, Co, Pd, Cu prefer the Ni-sites; (2) Sc, Y, Zr, Hf prefer the Ti-sites; (3) Zn and Cd can’t form a stable structure. In a martensitic phase transformation process, the bigger C44 /C’and stronger bonding interaction means the stronger transition resistance which lead to a lower transformation temperature. By analyzing the elastics modulus and the differential charge density map of NiTi, we can infer that: (1) the replace of Ni by the groups of V, Cr, Mn, Fe, Co or by Pd, Pt and replace of V, Cr, Mn, Fe for Ti will lower the transformation temperature; (2) Hf, Zr, Ag, Au substitute for Ni and Sc, Y, Hf, Zr substitute for Ti will increase the transformation temperature; (3) transformation temperature will almost be unchanged while Cu substitute for Ni. These results are consistent with the experimental ones and we can understand the influence of alloying elements on the phase transformation temperature of NiTi from the microscopic point of view.
The lattice parameters, formation energy, elastic modulus and differential charge density of NiTi alloyed by transition elements have been calculated by using the first principle method based on density functional theory (DFT). Then we can discuss the site preference of transition elements in NiTi and the influence of them on the martensitic transformation temperature of NiTi. The results show that, when added to NiTi Alloy: (1) the groups of V, Cr, Mn, Fe, Co, Pd, Cu prefer the Ni-sites; (2) Sc, Y, Zr, Hf prefer the Ti-sites; (3) Zn and Cd can’t form a stable structure. In a martensitic phase transformation process, the bigger C44 /C’and stronger bonding interaction means the stronger transition resistance which lead to a lower transformation temperature. By analyzing the elastics modulus and the differential charge density map of NiTi, we can infer that: (1) the replace of Ni by the groups of V, Cr, Mn, Fe, Co or by Pd, Pt and replace of V, Cr, Mn, Fe for Ti will lower the transformation temperature; (2) Hf, Zr, Ag, Au substitute for Ni and Sc, Y, Hf, Zr substitute for Ti will increase the transformation temperature; (3) transformation temperature will almost be unchanged while Cu substitute for Ni. These results are consistent with the experimental ones and we can understand the influence of alloying elements on the phase transformation temperature of NiTi from the microscopic point of view.
2016, 45(8):2046-2050.
Abstract:
Ni-Cr alloy coatings were obtained on mild carbon steel surface by direct current (DC) and pulse current (PC) electrodeposition. X-ray diffraction (XRD) analysis, scanning electron microscope (SEM) and atomic force microscope (AFM) were used to analyze the phase structure and surface morphology. The corrosion behaviors of Ni-Cr alloy coatings in the 3.5% (mass fraction) NaCl were investigated by soak method and electrochemical polarization method. The results show that microstructure and performance of the coatings were greatly affected by electrodeposition methods. The pulse electrodeposition can increase the amounts of new nuclei and reduce grain size, so the PC alloy coatings exhibit a relatively uniform and fine structure. The self-corrosion potential (Ecorr) of PC alloy coatings is increased from -0.624V to -0.477V and the corrosion current density (Icorr) is decreased from 1.911?0-4 A.cm-2 to 3.789?0-5 A.cm-2 compared to those of the DC alloy coatings. The PC alloy coatings have better corrosion resistance than DC alloy coatings.
Ni-Cr alloy coatings were obtained on mild carbon steel surface by direct current (DC) and pulse current (PC) electrodeposition. X-ray diffraction (XRD) analysis, scanning electron microscope (SEM) and atomic force microscope (AFM) were used to analyze the phase structure and surface morphology. The corrosion behaviors of Ni-Cr alloy coatings in the 3.5% (mass fraction) NaCl were investigated by soak method and electrochemical polarization method. The results show that microstructure and performance of the coatings were greatly affected by electrodeposition methods. The pulse electrodeposition can increase the amounts of new nuclei and reduce grain size, so the PC alloy coatings exhibit a relatively uniform and fine structure. The self-corrosion potential (Ecorr) of PC alloy coatings is increased from -0.624V to -0.477V and the corrosion current density (Icorr) is decreased from 1.911?0-4 A.cm-2 to 3.789?0-5 A.cm-2 compared to those of the DC alloy coatings. The PC alloy coatings have better corrosion resistance than DC alloy coatings.
2016, 45(8):2051-2056.
Abstract:
The effect of velocity on the dry sliding friction and wear characteristics of SiCp/A356 composite was investigated in detail on UMT-2 tribometer. The high temperature friction and wear behavior of the composite were analyzed by SEM, EDS and Olympus confocal laser scanning microscope. The results reveal that the wear rate of as-cast material is increased greatly and its friction coefficient fluctuates within a large range. On the contrary, the increasing degree of the wear rate and the friction coefficient of T6 material is low, which shows excellent friction behavior. the oxidation wear and stripping wear at low velocity of as-cast material is mainly shifted to adhesive wear at high velocity. However, the oxidation wear at low velocity of T6 material is mainly shifted to stripping wear and adrasive wear at high velocity. At high velocity, the crack appears obviously in the cross-section of worn surface of as-cast material, but there are only simple grinding traces and particle shedding in T6 material. Therefore, high temperature wear resistance of the composite has been improved significantly after heat treatment.
The effect of velocity on the dry sliding friction and wear characteristics of SiCp/A356 composite was investigated in detail on UMT-2 tribometer. The high temperature friction and wear behavior of the composite were analyzed by SEM, EDS and Olympus confocal laser scanning microscope. The results reveal that the wear rate of as-cast material is increased greatly and its friction coefficient fluctuates within a large range. On the contrary, the increasing degree of the wear rate and the friction coefficient of T6 material is low, which shows excellent friction behavior. the oxidation wear and stripping wear at low velocity of as-cast material is mainly shifted to adhesive wear at high velocity. However, the oxidation wear at low velocity of T6 material is mainly shifted to stripping wear and adrasive wear at high velocity. At high velocity, the crack appears obviously in the cross-section of worn surface of as-cast material, but there are only simple grinding traces and particle shedding in T6 material. Therefore, high temperature wear resistance of the composite has been improved significantly after heat treatment.
2016, 45(8):2057-2063.
Abstract:
The control of the temperature field during single crystal solidification has an important effect on single crystal growth. The present paper studied the influence of ceramic shell mold with central heat radiation on the microstructures and stress rupture property of the widely used DD6 single crystal superalloy. The results indicated that the mold with graphite center pillar could improve the uniformity of the temperature field and the temperature gradient during the solidification, and it could make the direction of heat flow more straight. As a result, the primary dendrite arm spacing decreased, the size and the volume fraction of γ-γ'' eutectic were reduced, the angle between the single crystal growth orientation and the [001] orientation decreased, so the single crystal superalloy can achieve longer stress rupture life.
The control of the temperature field during single crystal solidification has an important effect on single crystal growth. The present paper studied the influence of ceramic shell mold with central heat radiation on the microstructures and stress rupture property of the widely used DD6 single crystal superalloy. The results indicated that the mold with graphite center pillar could improve the uniformity of the temperature field and the temperature gradient during the solidification, and it could make the direction of heat flow more straight. As a result, the primary dendrite arm spacing decreased, the size and the volume fraction of γ-γ'' eutectic were reduced, the angle between the single crystal growth orientation and the [001] orientation decreased, so the single crystal superalloy can achieve longer stress rupture life.
2016, 45(8):2064-2070.
Abstract:
Transient liquid-phase bonding of magnesium alloy (AZ31B) to stainless steel (304) was performed using a copper interlayer. The microstructure and bonding strength of the bonded joint were studied. The results show that when the welding condition is 510℃×30min or 530℃×10min, no eutectic phase was observed in the welded joint and the metallurgical bond is weak. When the welding condition is 520℃×30min or 530℃×20min, the joint interface produces Mg-Cu eutectic. A significant increasing occurs in weld width and interfacial bonding strength increases too. At 530℃×30min, the magnesium matrix dissolves into the eutectic liquid , and the laminar diffusion region with a width of about 350μm forms in the welded joint at the magnesium side, besides,the interface forms a metallurgical bond relying on the Mg-Cu eutectic liquid wetting and spreading to the stainless steel surface. Microstructure followed by Mg-Cu eutectic layer, Mg-rich solid solution layer , Mg17(Cu,Al)12 dispersed in magnesium alloy matrix and permeability zones of Mg-Cu-Al ternary compounds distributed in grain boundaries of magnesium alloy. The shear strength of the joint reaches the highest value of (52MPa). With the welding condition of 540℃×30min or 530℃×40min, eutectic liquid on interfacial diffusion zone occurs isothermal solidification and the joint shear strength decreases, which attributed to continuous network distributed of Mg-Cu-Al compound along the magnesium grain boundary. Recrystallization and grain growth happens to AZ31B matrix, and twins produced at 530℃×30min. The second phase precipitates within the grains and significantly grows at 540℃×30min. AZ31B matrix appears different degrees of softening phenomenon.
Transient liquid-phase bonding of magnesium alloy (AZ31B) to stainless steel (304) was performed using a copper interlayer. The microstructure and bonding strength of the bonded joint were studied. The results show that when the welding condition is 510℃×30min or 530℃×10min, no eutectic phase was observed in the welded joint and the metallurgical bond is weak. When the welding condition is 520℃×30min or 530℃×20min, the joint interface produces Mg-Cu eutectic. A significant increasing occurs in weld width and interfacial bonding strength increases too. At 530℃×30min, the magnesium matrix dissolves into the eutectic liquid , and the laminar diffusion region with a width of about 350μm forms in the welded joint at the magnesium side, besides,the interface forms a metallurgical bond relying on the Mg-Cu eutectic liquid wetting and spreading to the stainless steel surface. Microstructure followed by Mg-Cu eutectic layer, Mg-rich solid solution layer , Mg17(Cu,Al)12 dispersed in magnesium alloy matrix and permeability zones of Mg-Cu-Al ternary compounds distributed in grain boundaries of magnesium alloy. The shear strength of the joint reaches the highest value of (52MPa). With the welding condition of 540℃×30min or 530℃×40min, eutectic liquid on interfacial diffusion zone occurs isothermal solidification and the joint shear strength decreases, which attributed to continuous network distributed of Mg-Cu-Al compound along the magnesium grain boundary. Recrystallization and grain growth happens to AZ31B matrix, and twins produced at 530℃×30min. The second phase precipitates within the grains and significantly grows at 540℃×30min. AZ31B matrix appears different degrees of softening phenomenon.
2016, 45(8):2071-2074.
Abstract:
Dense B4C matrix composites were synthesized by spark plasma sintering (SPS) process using CeO2 powders as the sintering aid. The effects of CeO2 on densification and properties of B4C were studied, and compared those with sample without additive. X-ray diffraction and transmission electron microscopy was employed to examine the phase and microstructure of the composites respectively. The results indicate that the addition of CeO2 powder can significantly improve the sintering propertyof B4C. The relative density of samples increased because of the existence of generated CeB6 between B4C grains. CeO2 content ranged from 1 wt.% to 8 wt.%. The specimen with 4 wt.% CeO2 sintered at 1750℃under a pressure of 35 MPa exhibited relative density of 96.7% and Rockwell hardness of 90.7HRA. Key words: boron carbide; cerium hexaboride; ceriumoxide; SPS; densification
Dense B4C matrix composites were synthesized by spark plasma sintering (SPS) process using CeO2 powders as the sintering aid. The effects of CeO2 on densification and properties of B4C were studied, and compared those with sample without additive. X-ray diffraction and transmission electron microscopy was employed to examine the phase and microstructure of the composites respectively. The results indicate that the addition of CeO2 powder can significantly improve the sintering propertyof B4C. The relative density of samples increased because of the existence of generated CeB6 between B4C grains. CeO2 content ranged from 1 wt.% to 8 wt.%. The specimen with 4 wt.% CeO2 sintered at 1750℃under a pressure of 35 MPa exhibited relative density of 96.7% and Rockwell hardness of 90.7HRA. Key words: boron carbide; cerium hexaboride; ceriumoxide; SPS; densification
30 Investigation on the arc erosion behavior of AgSnO2 contact materials with different SnO2 contents
2016, 45(8):2075-2079.
Abstract:
AgSnO2 contact materials with different SnO2 contents were prepared by powder metallurgy,and the effect of SnO2 content on the arc behavior of AgSnO2 contact materials was studied.The erosion surface morphology of AgSnO2 contact materials were characterized by scanning electron microscope,and the factors which affect arc erosion were discussed as well.The results shows that the arc erosion prefer to occur on SnO2 particles.The increased SnO2 content decreases the erosion area and deepens the erosion pits significantly,and,thus,has an obvious molten metal splash.
AgSnO2 contact materials with different SnO2 contents were prepared by powder metallurgy,and the effect of SnO2 content on the arc behavior of AgSnO2 contact materials was studied.The erosion surface morphology of AgSnO2 contact materials were characterized by scanning electron microscope,and the factors which affect arc erosion were discussed as well.The results shows that the arc erosion prefer to occur on SnO2 particles.The increased SnO2 content decreases the erosion area and deepens the erosion pits significantly,and,thus,has an obvious molten metal splash.
2016, 45(8):2080-2085.
Abstract:
Micro-arc oxidation(MAO) and hydrothermal synthesis(HS) methods were used to prepare hydroxyapatite（HA）, rutile and anatase TiO2 composite ceramic film on the surface of TA2 titanium．The experiment observed and analyzed morphology, elemental composition, phase composition and roughness of the film, and explored effect of hydrothermal time on characteristic and surface energy of the ceramic film on the surface of TA2 titanium. The results demonstrated that: after the hydrothermal treatment, large mounts of regular columnar and needle-like HA particles formed on the film, which is mainly consisted of such elements as Ti, O, Ca and P. With hydrothermal time prolonging, the HA particles were increased in number and volume, and surface roughness of the film went down at first, and then went up. At the initial stage of hydrothermal time surface energy of the film showed upward trend with the decrease of surface roughness. The contact angle of water on the film, between 116.0 ° ~ 140.2 °, was larger than that of water on TA2 titanium, which implied that hydrophobicity of the film is enhanced. Compared with TA2 titanium, surface energy of the film which is between 150.7 mJ ? m-2 ~ 282.9 mJ ? m-2, increased more than four times, with the change of its roughness being the major factor.
Micro-arc oxidation(MAO) and hydrothermal synthesis(HS) methods were used to prepare hydroxyapatite（HA）, rutile and anatase TiO2 composite ceramic film on the surface of TA2 titanium．The experiment observed and analyzed morphology, elemental composition, phase composition and roughness of the film, and explored effect of hydrothermal time on characteristic and surface energy of the ceramic film on the surface of TA2 titanium. The results demonstrated that: after the hydrothermal treatment, large mounts of regular columnar and needle-like HA particles formed on the film, which is mainly consisted of such elements as Ti, O, Ca and P. With hydrothermal time prolonging, the HA particles were increased in number and volume, and surface roughness of the film went down at first, and then went up. At the initial stage of hydrothermal time surface energy of the film showed upward trend with the decrease of surface roughness. The contact angle of water on the film, between 116.0 ° ~ 140.2 °, was larger than that of water on TA2 titanium, which implied that hydrophobicity of the film is enhanced. Compared with TA2 titanium, surface energy of the film which is between 150.7 mJ ? m-2 ~ 282.9 mJ ? m-2, increased more than four times, with the change of its roughness being the major factor.
2016, 45(8):2086-2091.
Abstract:
5052/AZ31/5052 tri-layer clad sheet is a new material with energy saving and consumption reduction. It is of vital significance to study its formibility for its wide applications in industrial field. The forming limit curves of 5052Al/AZ31Mg/5052Al tri-layer clad sheet at 170℃ and 230℃ were obtained respectively by using hemispherical punch. Fracture morphology at limit position and the interface diffusion behavior during bulging process were studied. The results showed that: 5052Al/AZ31Mg/5052Al tri-layer clad sheet has a superior formability at 230℃; the bulging process promoted magnesium and aluminum elements near the bond interface distributed homogeneously and had little effect on the thickness of diffusion layer; the defects were eliminated and the mechanical occlusion areas of bond interface were increased by the bulging process, which is beneficial to improve the bond strength of the interface.
5052/AZ31/5052 tri-layer clad sheet is a new material with energy saving and consumption reduction. It is of vital significance to study its formibility for its wide applications in industrial field. The forming limit curves of 5052Al/AZ31Mg/5052Al tri-layer clad sheet at 170℃ and 230℃ were obtained respectively by using hemispherical punch. Fracture morphology at limit position and the interface diffusion behavior during bulging process were studied. The results showed that: 5052Al/AZ31Mg/5052Al tri-layer clad sheet has a superior formability at 230℃; the bulging process promoted magnesium and aluminum elements near the bond interface distributed homogeneously and had little effect on the thickness of diffusion layer; the defects were eliminated and the mechanical occlusion areas of bond interface were increased by the bulging process, which is beneficial to improve the bond strength of the interface.
33 Influences on properties of AZ91D composite ceramic layer formed in electrolyte adding Al2O3 colloid
2016, 45(8):2092-2097.
Abstract:
Ceramic coating was fabricated on AZ91D magnesium alloys by micro-arc oxidation in silicate system which was added Al2O3 colloid, influences of adding time and amount on chemical composition, microstructure and corrosion resistance of the MAO ceramic coatings were studied. The results showed that the ceramic coating which was formed by adding Al2O3 colloid at about 6min (the total oxidation time was 10min) performed the best corrosion resistance; and the corrosion rate was reduced evidently with the increase of Al2O3 colloid dosage, however, the performance of corrosion resistance was hardly influenced when used excessive dosage
Ceramic coating was fabricated on AZ91D magnesium alloys by micro-arc oxidation in silicate system which was added Al2O3 colloid, influences of adding time and amount on chemical composition, microstructure and corrosion resistance of the MAO ceramic coatings were studied. The results showed that the ceramic coating which was formed by adding Al2O3 colloid at about 6min (the total oxidation time was 10min) performed the best corrosion resistance; and the corrosion rate was reduced evidently with the increase of Al2O3 colloid dosage, however, the performance of corrosion resistance was hardly influenced when used excessive dosage
2016, 45(8):2098-2103.
Abstract:
An experimental set-up was designed for the fabrication of composite coating containg titania and Ag on the surface of titanium and make the titanium has bioactive and antibacterial synchronously. The SEM, XRD, bioactive test and antibacterial test were imployed to researched that how the method of the heat treatment work on the formation and capability of the titania-Ag composite coating. The results show that titanium with titania nanotube arrays diped in the saturated silver nitrate solution and heated under 500癈 or 600癈, the titanium can obtain bioactive and antibacterial synchronously because of the existence of titania-Ag composite coating.
An experimental set-up was designed for the fabrication of composite coating containg titania and Ag on the surface of titanium and make the titanium has bioactive and antibacterial synchronously. The SEM, XRD, bioactive test and antibacterial test were imployed to researched that how the method of the heat treatment work on the formation and capability of the titania-Ag composite coating. The results show that titanium with titania nanotube arrays diped in the saturated silver nitrate solution and heated under 500癈 or 600癈, the titanium can obtain bioactive and antibacterial synchronously because of the existence of titania-Ag composite coating.
2016, 45(8):2104-2110.
Abstract:
The effects of grain size inhomogeniety in large size ingot on hot deformation behaviors of a new high strength Al-7.68Zn-2.12Mg-1.98Cu-0.12Zr alloy were investigated using Gleeble-3500 test machine at 300–450℃ with strain rates from 0.1 to 10 s-1.SEM observation showed that the grain size in surface layer of ingot was finer than that in central layer. During hot deformation, the low stress of the sample with fine grain(surface layer) was lower than that of the sample with coarse grain(central layer)at high temperature and low strain rate conditions. The hot deformation activation energies(Q) of 140kJ/mol and 125.4kJ/mol were obtained for fine grain microstructure and coarse grain microstructure respectively. Thelow stresses were predicted by a two-stage type constitutive model based on the dislocation density theory, and the dynamic recrystallization soften equations were established for the microstructures of fine grain and coarse grain. Electron Back-Scattered Diffraction(EBSD) observations revealed that the alloy exhibited dynamic recovery at temperatures ranging from 300 to 400℃ and dynamic recrystallization(DRX) at 450℃ with low strain rate(≤0.1s-1).The DRX grains nucleated at the original grainSboundaries. It was found that the DRX fracture was higher in finer grain (surface layer)microstructure resulting from the higher grain boundary density.
The effects of grain size inhomogeniety in large size ingot on hot deformation behaviors of a new high strength Al-7.68Zn-2.12Mg-1.98Cu-0.12Zr alloy were investigated using Gleeble-3500 test machine at 300–450℃ with strain rates from 0.1 to 10 s-1.SEM observation showed that the grain size in surface layer of ingot was finer than that in central layer. During hot deformation, the low stress of the sample with fine grain(surface layer) was lower than that of the sample with coarse grain(central layer)at high temperature and low strain rate conditions. The hot deformation activation energies(Q) of 140kJ/mol and 125.4kJ/mol were obtained for fine grain microstructure and coarse grain microstructure respectively. Thelow stresses were predicted by a two-stage type constitutive model based on the dislocation density theory, and the dynamic recrystallization soften equations were established for the microstructures of fine grain and coarse grain. Electron Back-Scattered Diffraction(EBSD) observations revealed that the alloy exhibited dynamic recovery at temperatures ranging from 300 to 400℃ and dynamic recrystallization(DRX) at 450℃ with low strain rate(≤0.1s-1).The DRX grains nucleated at the original grainSboundaries. It was found that the DRX fracture was higher in finer grain (surface layer)microstructure resulting from the higher grain boundary density.
2016, 45(8):2111-2115.
Abstract:
Effects of Cu85Sn15 intergranular additions on the magnetic and anti-corrosion properties of (Pr,Nd)12.6Dy0.9FebalB5.9 were investigated. Results showed that when 0.16 wt% Cu85Sn15 was added, the NdFeB magnet possessed the maixum values of the magnetic properties and anti-corrosion resistance. The improvement of corrosion resistance mainly arose from the increase in the density and from the optimized distribution of intergranular phases. Also the aforementioned optimization of structure factors benefited the anti-corrosion performance of NdFeB. Additionally, in the Cu85Sn15 doped magnet the occurrence of (Pr,Nd)6Fe13Cu and the decrease in the amount of (Pr, Nd)-rich phase reduced the formation of active reaction channels in the anodic intergranular regions, thus increasing the charge transfer resistance. As a result, the corrosion current density decreased and the corrosion resistance was enhanced.
Effects of Cu85Sn15 intergranular additions on the magnetic and anti-corrosion properties of (Pr,Nd)12.6Dy0.9FebalB5.9 were investigated. Results showed that when 0.16 wt% Cu85Sn15 was added, the NdFeB magnet possessed the maixum values of the magnetic properties and anti-corrosion resistance. The improvement of corrosion resistance mainly arose from the increase in the density and from the optimized distribution of intergranular phases. Also the aforementioned optimization of structure factors benefited the anti-corrosion performance of NdFeB. Additionally, in the Cu85Sn15 doped magnet the occurrence of (Pr,Nd)6Fe13Cu and the decrease in the amount of (Pr, Nd)-rich phase reduced the formation of active reaction channels in the anodic intergranular regions, thus increasing the charge transfer resistance. As a result, the corrosion current density decreased and the corrosion resistance was enhanced.
2016, 45(8):2116-2122.
Abstract:
To improve the corrosion resistance and biocompatibility of magnesium alloys, Ca-P coatings were fabricated on the fluoride-treated AZ31 magnesium by way of electrochemical deposition. Before the electrochemical deposition, the fluoride-treated AZ31 magnesium was immersed in Ca(OH)2 solution to modified the surfaceSofSfluoride conversion film . The morphology, composition and structure of the samples were investigated by SEM, EDS, XRD and FTIR, respectively. The results showed that the MgF2 conversion film with micro-pores was formed on AZ31 alloy through the fluoride treatment. After soaking in Ca(OH)2, CaF2 film with miicro/nano pores was formed on the fluoride-treated surface, which is advantageous toStheSnucleation of calcium phosphate. The Ca-P coating deposited on Ca(OH)2-immersioned sample was more uniform and compact than the untreated one. The coating was composed of flake-like crystals of brushite (DCPD,CaHPO4.2H2O) with about 70 μm length and 30μm width and converted to hydroxyapatite(HA ) coating which was covered bySvillous deposition after alkaline-heat treatment.
To improve the corrosion resistance and biocompatibility of magnesium alloys, Ca-P coatings were fabricated on the fluoride-treated AZ31 magnesium by way of electrochemical deposition. Before the electrochemical deposition, the fluoride-treated AZ31 magnesium was immersed in Ca(OH)2 solution to modified the surfaceSofSfluoride conversion film . The morphology, composition and structure of the samples were investigated by SEM, EDS, XRD and FTIR, respectively. The results showed that the MgF2 conversion film with micro-pores was formed on AZ31 alloy through the fluoride treatment. After soaking in Ca(OH)2, CaF2 film with miicro/nano pores was formed on the fluoride-treated surface, which is advantageous toStheSnucleation of calcium phosphate. The Ca-P coating deposited on Ca(OH)2-immersioned sample was more uniform and compact than the untreated one. The coating was composed of flake-like crystals of brushite (DCPD,CaHPO4.2H2O) with about 70 μm length and 30μm width and converted to hydroxyapatite(HA ) coating which was covered bySvillous deposition after alkaline-heat treatment.
2016, 45(8):2123-2127.
Abstract:
A combination of transmission electron microscopy, scanning electron microscopy and optical microscopy was used to study deformation and fracture behaviors of lamellar microstructure (LM) Ti-55531 alloy during tensile and torsion tests at room temperature. Results indicate that loading modes have a significant influence on deformation and fracture mechanisms of LM Ti-55531 alloy. First of all, the tensile stress-strain curve of LM Ti-55531 alloy is different from its torsion stress-strain curve. The stress could decline at the end stage of the tensile test, while it is not during the torsion experiment. Secondly, deformation mechanism of tensile test is a mix mode which combines dislocation slip, twinning and shear of secondary αs phase, while deformation of torsion test are controlled predominantly by dislocation slips and shear. Thirdly, fractographs of tensile and torsion tested specimens seem to possess different morphologies. Fractographs of tensile specimens are cliffier than torsion specimens. The tensile samples show a ductile failure, including dimple, cleavage and inter-granular fracture mechanisms. The fracture of torsion specimen is still a mix mode type but with more shear dimples. At last but not the least, no matter samples under tensile or torsion loading, the failure of LM Ti-55531 alloy are controlled by the highest shear stress. And the shear stress has much more influence on the failure of LM Ti-55531 alloy than the rectangle stress.
A combination of transmission electron microscopy, scanning electron microscopy and optical microscopy was used to study deformation and fracture behaviors of lamellar microstructure (LM) Ti-55531 alloy during tensile and torsion tests at room temperature. Results indicate that loading modes have a significant influence on deformation and fracture mechanisms of LM Ti-55531 alloy. First of all, the tensile stress-strain curve of LM Ti-55531 alloy is different from its torsion stress-strain curve. The stress could decline at the end stage of the tensile test, while it is not during the torsion experiment. Secondly, deformation mechanism of tensile test is a mix mode which combines dislocation slip, twinning and shear of secondary αs phase, while deformation of torsion test are controlled predominantly by dislocation slips and shear. Thirdly, fractographs of tensile and torsion tested specimens seem to possess different morphologies. Fractographs of tensile specimens are cliffier than torsion specimens. The tensile samples show a ductile failure, including dimple, cleavage and inter-granular fracture mechanisms. The fracture of torsion specimen is still a mix mode type but with more shear dimples. At last but not the least, no matter samples under tensile or torsion loading, the failure of LM Ti-55531 alloy are controlled by the highest shear stress. And the shear stress has much more influence on the failure of LM Ti-55531 alloy than the rectangle stress.
Xie Donghua
,
Lai Xinchun
,
Tan Shiyong
,
Zhang Wen
,
Liu Yi
,
Feng Wei
,
Zhang Yun
,
Liu Qing
,
Zhu Xiegang
,
Yuan Bingkai
,
Fang Yun
2016, 45(8):2128-2132.
Abstract:
High-quality single crystals of USb2 were grown by the Sb self-flux method. The magnetic susceptibility, resistivity, magnetoresistance and specific heat were measured. The results indicate that, the 5f electrons in USb2 with moderately correlated electron system exhibit dual characteristics of both localized and itinerant behaviors. The 5f electrons of USb2 begin to coherent about 260 K. USb2 transforms from paramagnetic into antiferromagnetic state at 203 K and the reconstruction of the Fermi surface occurs. The electronic structure near Fermi surface is further changed through the first hybridization between the localized 5f electrons and the conduction electrons below 113 K. The second hybridization leads to open one energy gap near the Fermi surface below 54 K. The crystal field effects have an important impact on physical properties at lower temperatures.
High-quality single crystals of USb2 were grown by the Sb self-flux method. The magnetic susceptibility, resistivity, magnetoresistance and specific heat were measured. The results indicate that, the 5f electrons in USb2 with moderately correlated electron system exhibit dual characteristics of both localized and itinerant behaviors. The 5f electrons of USb2 begin to coherent about 260 K. USb2 transforms from paramagnetic into antiferromagnetic state at 203 K and the reconstruction of the Fermi surface occurs. The electronic structure near Fermi surface is further changed through the first hybridization between the localized 5f electrons and the conduction electrons below 113 K. The second hybridization leads to open one energy gap near the Fermi surface below 54 K. The crystal field effects have an important impact on physical properties at lower temperatures.
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.
2016, 45(8):2146-2149.
Abstract:
The plate-like grain cemented carbides were prepared using W Co C (carbon black) as the raw materials. Effects of the morphologies of tungsten powders prepared by different raw materials on the flattening morphologies of W powders and the microstructures and properties of plate-like grain cemented carbides were researched. It showed that the morphologies of W powders prepared by blue tungsten oxides (BTO) were spherical polyhedron. However, the W powders prepared by yellow tungsten oxides (YTO) were polyhedral equiaxial, which were easier access to prepare plate-like tungsten powders by ball milling, and prepare plate-like grain WC-Co cemented carbides.
The plate-like grain cemented carbides were prepared using W Co C (carbon black) as the raw materials. Effects of the morphologies of tungsten powders prepared by different raw materials on the flattening morphologies of W powders and the microstructures and properties of plate-like grain cemented carbides were researched. It showed that the morphologies of W powders prepared by blue tungsten oxides (BTO) were spherical polyhedron. However, the W powders prepared by yellow tungsten oxides (YTO) were polyhedral equiaxial, which were easier access to prepare plate-like tungsten powders by ball milling, and prepare plate-like grain WC-Co cemented carbides.
2016, 45(8):2150-2154.
Abstract:
The effects of electric pulse heat treatment on microstructures and mechanical properties of hot-rolled equiaxed TC4 alloy were investigated. It is interesting to find that, the original equiaxed microstructure of hot-rolled TC4 alloy was turned to the typical lamellar microstructure within 5min, and the minutes spent for microstructure transformation show decreasing tendency with the increased heat treatment temperature; recrystallization happened to the equiaxed microstructure before microstructure transformation, after microstructure transformation, the prior beta grains size showed an increasing tendency with temperature and maintaining time. The results of quasi-static and dynamic compression tests showed that, compared with the original hot-rolled TC4 alloy, the fracture strain value of alloys after electric pulse heat (EPH) treatment was significantly improved while the susceptibility to the adiabatic shear bands (ASBs) of the hot-rolled TC4 titanium alloy was obviously declined as well, and the fracture strain value of alloys after electric pulse heat (EPH) treatment showed decreasing tendency with the increased temperature and maintaining time. Compared with the original hot-rolled titanium alloy, the adiabatic shear fracture strain of the alloy which was treated at 1000℃ for 5min increased by 133%, and the energy absorbed by materials before adiabatic shear failure increased by 192%.
The effects of electric pulse heat treatment on microstructures and mechanical properties of hot-rolled equiaxed TC4 alloy were investigated. It is interesting to find that, the original equiaxed microstructure of hot-rolled TC4 alloy was turned to the typical lamellar microstructure within 5min, and the minutes spent for microstructure transformation show decreasing tendency with the increased heat treatment temperature; recrystallization happened to the equiaxed microstructure before microstructure transformation, after microstructure transformation, the prior beta grains size showed an increasing tendency with temperature and maintaining time. The results of quasi-static and dynamic compression tests showed that, compared with the original hot-rolled TC4 alloy, the fracture strain value of alloys after electric pulse heat (EPH) treatment was significantly improved while the susceptibility to the adiabatic shear bands (ASBs) of the hot-rolled TC4 titanium alloy was obviously declined as well, and the fracture strain value of alloys after electric pulse heat (EPH) treatment showed decreasing tendency with the increased temperature and maintaining time. Compared with the original hot-rolled titanium alloy, the adiabatic shear fracture strain of the alloy which was treated at 1000℃ for 5min increased by 133%, and the energy absorbed by materials before adiabatic shear failure increased by 192%.
2016, 45(8):2155-2160.
Abstract:
Under the monitoring of the universal testing machine platform, ZrC ceramics were prepared by self-propagating high-temperature synthesis/single action pressing (SHS/SAP) dynamic combing self-propagating high-temperature synthesis /pseudo–hot isostatic pressing (SHS/PHIP). The relationship between rules of displacement, load curve changing and technology parameters of SHS/PHIP plus the effects of pressure on microstructure and densification of the products were studied. Displacement and load curve were recorded by the universal testing machine platform, using XRD and SEM to demonstrate the phase constitution and microstructure of products, and the density was measured by the drain away liquid way. Our results indicate that the ended time of SHS reaction and the plasticity period of time of products were demonstrated by displacement and load curves, which can be used as parameters of pressure applying moment and dwell time of SHS/PHIP. With the increasing pressure, extrusion deformation of ZrC grain surface was more obviously, leading to the sintering necks in the pressur of 120MPa. Density was increased along with the pressure and with a peak of 93.7%, and the involved mechanism includes crystal particles rearrangement and plastic defomation.
Under the monitoring of the universal testing machine platform, ZrC ceramics were prepared by self-propagating high-temperature synthesis/single action pressing (SHS/SAP) dynamic combing self-propagating high-temperature synthesis /pseudo–hot isostatic pressing (SHS/PHIP). The relationship between rules of displacement, load curve changing and technology parameters of SHS/PHIP plus the effects of pressure on microstructure and densification of the products were studied. Displacement and load curve were recorded by the universal testing machine platform, using XRD and SEM to demonstrate the phase constitution and microstructure of products, and the density was measured by the drain away liquid way. Our results indicate that the ended time of SHS reaction and the plasticity period of time of products were demonstrated by displacement and load curves, which can be used as parameters of pressure applying moment and dwell time of SHS/PHIP. With the increasing pressure, extrusion deformation of ZrC grain surface was more obviously, leading to the sintering necks in the pressur of 120MPa. Density was increased along with the pressure and with a peak of 93.7%, and the involved mechanism includes crystal particles rearrangement and plastic defomation.
2016, 45(8):2161-2164.
Abstract:
Silver nanoparticles have been synthesized by the reduction of AgNO3 in the presence of polyvinyl pyrrolidone as surfactant and ethylene glycol as reducing agent through a hot-injection method. The size distribution, morphology, structure and optical properties of particles have been characterized by transmission electron microscopy (TEM), X-ray diffractometer (XRD) and UV/Visible absorption spectrophotometry. While the absorption spectra was investigated by means of Mie theory. Results indicate that comparing to the traditional one-step reduction routes, the silver nanoparticles, derived from hot-injection method, possesses a better dispersion and more uniform size distribution. TEM images show that the morphology of nano-silver particles are spheroidal, with an average diameter of 20 nm, and the experimental observations are basically consistent with the numerical analysis results.
Silver nanoparticles have been synthesized by the reduction of AgNO3 in the presence of polyvinyl pyrrolidone as surfactant and ethylene glycol as reducing agent through a hot-injection method. The size distribution, morphology, structure and optical properties of particles have been characterized by transmission electron microscopy (TEM), X-ray diffractometer (XRD) and UV/Visible absorption spectrophotometry. While the absorption spectra was investigated by means of Mie theory. Results indicate that comparing to the traditional one-step reduction routes, the silver nanoparticles, derived from hot-injection method, possesses a better dispersion and more uniform size distribution. TEM images show that the morphology of nano-silver particles are spheroidal, with an average diameter of 20 nm, and the experimental observations are basically consistent with the numerical analysis results.
2016, 45(8):2165-2168.
Abstract:
The hydroxy-iron powder with a hollow structure（h-hydroxy-iron，h-HI）were prepared with pitting method, then hollow-HI coated with MWCNTs(MWCNTs@h-HI) were prepared by connecting h-HI and MWCNTs with PABA as the active grafting agent. XRD、SEM、TEM Lakeshore7307VSM were used to characterize the as-prepared products, Hydroxy-iron powder, hollow HI and MWCNTs@HI were also characterized as comparisons. The experimental results showed that the hydroxy-iron powder was successfully prepared and grafted with MWCNTs, the best pitting time was 15min, the wall thicknesses of h-HI particles were 200nm and the thickness of grafting layer were 150nm when the diameters of h-HI particles were about 2μm. The saturation magnetization (Ms) of MWCNTs@h-HI was 140.88emu/g, the remanence(Mr) was 1.48emu/g and the coercivity(Hc) was 47.42G.
The hydroxy-iron powder with a hollow structure（h-hydroxy-iron，h-HI）were prepared with pitting method, then hollow-HI coated with MWCNTs(MWCNTs@h-HI) were prepared by connecting h-HI and MWCNTs with PABA as the active grafting agent. XRD、SEM、TEM Lakeshore7307VSM were used to characterize the as-prepared products, Hydroxy-iron powder, hollow HI and MWCNTs@HI were also characterized as comparisons. The experimental results showed that the hydroxy-iron powder was successfully prepared and grafted with MWCNTs, the best pitting time was 15min, the wall thicknesses of h-HI particles were 200nm and the thickness of grafting layer were 150nm when the diameters of h-HI particles were about 2μm. The saturation magnetization (Ms) of MWCNTs@h-HI was 140.88emu/g, the remanence(Mr) was 1.48emu/g and the coercivity(Hc) was 47.42G.
2016, 45(8):2169-2175.
Abstract:
Magnesium foams are fabricated by melt foaming method using coated CaCO3 as blowing agent. Macro-micro structure characteristics of magnesium foams are investigated by OM, SEM, EDS and XRD methods. The results show that the macro pores are given priority to with closed-cell structure. Meanwhile it contains some communicated pores and big pores, these positions usually generate macro cracks during compression. Fold defects and reaction products MgO and CaO particles diffusely distribute on the pore inner walls, create stress concentration and cause micro cracks. Pore walls are mainly composed of SiC particles introduced at the thickening stage and second phases Mg2Ca. Furthermore, compressive properties and energy absorption performances are tested and the fracture mechanism is studied. Elastic deformation and yield strength increase with decreasing porosity. Yield strength and plateau stress reduce dramatically with increasing pore size, namely magnesium foam shows an evident aperture effect. Besides, energy absorption performances significantly decrease with increasing porosity or pore size. And magnesium foam shows cleavage fracture during compression due to the micro structure of pore walls and the characteristic of magnesium substrate.
Magnesium foams are fabricated by melt foaming method using coated CaCO3 as blowing agent. Macro-micro structure characteristics of magnesium foams are investigated by OM, SEM, EDS and XRD methods. The results show that the macro pores are given priority to with closed-cell structure. Meanwhile it contains some communicated pores and big pores, these positions usually generate macro cracks during compression. Fold defects and reaction products MgO and CaO particles diffusely distribute on the pore inner walls, create stress concentration and cause micro cracks. Pore walls are mainly composed of SiC particles introduced at the thickening stage and second phases Mg2Ca. Furthermore, compressive properties and energy absorption performances are tested and the fracture mechanism is studied. Elastic deformation and yield strength increase with decreasing porosity. Yield strength and plateau stress reduce dramatically with increasing pore size, namely magnesium foam shows an evident aperture effect. Besides, energy absorption performances significantly decrease with increasing porosity or pore size. And magnesium foam shows cleavage fracture during compression due to the micro structure of pore walls and the characteristic of magnesium substrate.
2016, 45(8):2176-2181.
Abstract:
Abstract： The some parameters of preparation ethanolamine hydroxyl platinum(Ⅳ), such as concentration of platinum, the amount of oxidant and sodium hydroxide, was tested by means of single factors experiment design, and optimized by response surface method. and then established an empirical mathematical model for to predict yield of ethanolamine hydroxyl platinum(Ⅳ). The results demonstrated that the significance of influence factor as followed the order, platinum concentration＞oxidant amount＞NaOH amount. The yield(89.625%)of ethanolamine hydroxyl platinum(Ⅳ) could be obtained under the optimized conditions, platinum concentration 100g.L-1, oxidant amount 10%, and NaOH amount 2.25 times(in mass). The results show that the empirical mathematical model was feasible for the optimized parameters to prepare ethanolamine hydroxyl platinum(Ⅳ) and also to predict its yield. The structural formula of the compounds was verified of (NH3CH2CH2OH)2Pt(OH)6 by the sample characterization.
Abstract： The some parameters of preparation ethanolamine hydroxyl platinum(Ⅳ), such as concentration of platinum, the amount of oxidant and sodium hydroxide, was tested by means of single factors experiment design, and optimized by response surface method. and then established an empirical mathematical model for to predict yield of ethanolamine hydroxyl platinum(Ⅳ). The results demonstrated that the significance of influence factor as followed the order, platinum concentration＞oxidant amount＞NaOH amount. The yield(89.625%)of ethanolamine hydroxyl platinum(Ⅳ) could be obtained under the optimized conditions, platinum concentration 100g.L-1, oxidant amount 10%, and NaOH amount 2.25 times(in mass). The results show that the empirical mathematical model was feasible for the optimized parameters to prepare ethanolamine hydroxyl platinum(Ⅳ) and also to predict its yield. The structural formula of the compounds was verified of (NH3CH2CH2OH)2Pt(OH)6 by the sample characterization.
2016, 45(8):2182-2188.
Abstract:
In order to improve the resistance of titanium alloy on the tribological characteristics, laser processing was used to build grid and dot micro-structure with spacing of 100μm and 300μm on Ti6Al4V alloy surface. The Nano-SiO2 powders were coated on the micro-structures to build micro-nano structures. The contact angles and roll angles were measured by contact angle measurement. The micrograph and wear tracks were investigated by LEXT OLS4000 3D microscope. Tribological performance were evaluated by CETR Universal Micro-Tribometer(UMT). The results show that the micro structure surface is in hydrophobic state that is in accordance with Wenzel model, while the surfaces with the micro-nano structure formed by coating the Nano-SiO2 is in super hydrophobic state that is in accordance with Cassie model. With the increase of spacing, the surface is more easily to be wet. The dot surface is more easily to be wet than grid surface. When the load is 50 mN, friction-reducing and wear protection of the surface enhance with weaken of surface wettability. When the load is 5 N, coating SiO2 can enhance wear resistance and friction-reducing of the surface significantly, while wear resistance of the gird surface is stronger than that of the dot.
In order to improve the resistance of titanium alloy on the tribological characteristics, laser processing was used to build grid and dot micro-structure with spacing of 100μm and 300μm on Ti6Al4V alloy surface. The Nano-SiO2 powders were coated on the micro-structures to build micro-nano structures. The contact angles and roll angles were measured by contact angle measurement. The micrograph and wear tracks were investigated by LEXT OLS4000 3D microscope. Tribological performance were evaluated by CETR Universal Micro-Tribometer(UMT). The results show that the micro structure surface is in hydrophobic state that is in accordance with Wenzel model, while the surfaces with the micro-nano structure formed by coating the Nano-SiO2 is in super hydrophobic state that is in accordance with Cassie model. With the increase of spacing, the surface is more easily to be wet. The dot surface is more easily to be wet than grid surface. When the load is 50 mN, friction-reducing and wear protection of the surface enhance with weaken of surface wettability. When the load is 5 N, coating SiO2 can enhance wear resistance and friction-reducing of the surface significantly, while wear resistance of the gird surface is stronger than that of the dot.
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 .
