Volume 46,Issue 10,2017 Table of Contents
1 Dynamic behavior and constitutive model for two tantalum-tungsten alloys under elevated strain rates
2017, 46(10):2753-2762.
Abstract:
In this paper, a systematic investigation on the quasi-static and dynamic deformation behavior of two tantalum-tungsten (Ta-W) alloys, namely Ta-2.5 weight percentage W (Ta-2.5W) and Ta-10 weight percentage W (Ta-10W), is presented. It is shown based on the performed SHPB and Taylor impact tests that the yield stresses of tantalum-tungsten alloys exhibit sensitivity to strain rate and W content. Based on the quasi-static and high strain-rate experimental data, the material constants in Johnson-Cook (JC) model were obtained for the two Ta-W alloys. In addition, validation of the derived constitutive model is carried out through comparison of Taylor impact inhomogeneous deformations under high strain rate (103~104 s-1), obtained from simulations, with their experimental counterparts. It is shown that the simulation results agree well with post-test geometries in terms of side profiles and impact-interface footprints for Taylor impact tests. To bridge the different spatial scale involved in the process of tantalum-tungsten alloy deformation, a meso-scale research is proposed via a optical microscope (OM) image analysis. The results presented in this paper, provide new insights into the mechanisms suitable for the constitutive relations determination process.
In this paper, a systematic investigation on the quasi-static and dynamic deformation behavior of two tantalum-tungsten (Ta-W) alloys, namely Ta-2.5 weight percentage W (Ta-2.5W) and Ta-10 weight percentage W (Ta-10W), is presented. It is shown based on the performed SHPB and Taylor impact tests that the yield stresses of tantalum-tungsten alloys exhibit sensitivity to strain rate and W content. Based on the quasi-static and high strain-rate experimental data, the material constants in Johnson-Cook (JC) model were obtained for the two Ta-W alloys. In addition, validation of the derived constitutive model is carried out through comparison of Taylor impact inhomogeneous deformations under high strain rate (103~104 s-1), obtained from simulations, with their experimental counterparts. It is shown that the simulation results agree well with post-test geometries in terms of side profiles and impact-interface footprints for Taylor impact tests. To bridge the different spatial scale involved in the process of tantalum-tungsten alloy deformation, a meso-scale research is proposed via a optical microscope (OM) image analysis. The results presented in this paper, provide new insights into the mechanisms suitable for the constitutive relations determination process.
2017, 46(10):2763-2769.
Abstract:
Study focused on the magnesium alloy hot rolling process. A method was proposed to determine the friction coefficient in process through the comparative analysis of finite element analysis result and experimental data. Mathematical model for solving the friction coefficient was established, combining with multi-parameters of the rolling process: rolling temperature, rolling speed and reduction rate. Based on calculation model of rolling force and temperature distribution along the contact region in hot rolling of AZ31B magnesium alloy in previous research, rolling force prediction model was optimized and reconstructed considering the normal pressure and friction stress comprehensively. The contact friction stress and its influence on rolling force with an approximate percentage of 4.36% was defined.
Study focused on the magnesium alloy hot rolling process. A method was proposed to determine the friction coefficient in process through the comparative analysis of finite element analysis result and experimental data. Mathematical model for solving the friction coefficient was established, combining with multi-parameters of the rolling process: rolling temperature, rolling speed and reduction rate. Based on calculation model of rolling force and temperature distribution along the contact region in hot rolling of AZ31B magnesium alloy in previous research, rolling force prediction model was optimized and reconstructed considering the normal pressure and friction stress comprehensively. The contact friction stress and its influence on rolling force with an approximate percentage of 4.36% was defined.
2017, 46(10):2770-2774.
Abstract:
The rapid increase of the demand for titanium and titanium alloy rods with high strength and fine ductility results in the necessity to develop a multi-roller mill and a hot continuous rolling process. In this study, the authors propose to produce TC4 alloy rod on Y-type mill with a multi-line triangle-round pass system. The deformation feature, rolling stability, and temperature distribution of TC4 alloy rod during the hot continuous rolling process are simulated with ANSYS software. The experiments are also conducted on Y-type mill. The results show that the multi-line triangle pass with concavity has a good centrality. Thus, the system can prevent TC4 rod to twist or deviate from the rolling direction, and the stability of the rolled rod can be improved. Compared with the conventional flat triangle-round pass system, the proposed pass system obviously decreases the temperature gradient along the cross section of TC4 rod, thereby reducing the possibility of surface cracking, and improving the surface quality of the final product.
The rapid increase of the demand for titanium and titanium alloy rods with high strength and fine ductility results in the necessity to develop a multi-roller mill and a hot continuous rolling process. In this study, the authors propose to produce TC4 alloy rod on Y-type mill with a multi-line triangle-round pass system. The deformation feature, rolling stability, and temperature distribution of TC4 alloy rod during the hot continuous rolling process are simulated with ANSYS software. The experiments are also conducted on Y-type mill. The results show that the multi-line triangle pass with concavity has a good centrality. Thus, the system can prevent TC4 rod to twist or deviate from the rolling direction, and the stability of the rolled rod can be improved. Compared with the conventional flat triangle-round pass system, the proposed pass system obviously decreases the temperature gradient along the cross section of TC4 rod, thereby reducing the possibility of surface cracking, and improving the surface quality of the final product.
Dou Ya-kun
,
Feng Yi
,
Huang Xiao-chen
,
Tang Hai
,
Ding Dong-dong
,
Tian Pei
,
Xia Meng
,
Qian Gang
,
Zhang Xue-bin
2017, 46(10):2775-2780.
Abstract:
A thorough of thermoplastic polymer in the wax-based binder is essential for ensuring the dimensions and mechanical properties of 316L stainless steel metal injection molding parts. The effects of three thermoplastic polymers, High density polyethylene, High density polyethylene /Polypropylene and Polypropylene, on the dimensions and mechanical properties of 316L stainless steel metal injection molding parts have been compared in this paper. The tensile bar is tested to examine the dimensions and mechanical properties of sintered parts against different thermoplastic polymers in the binder. Among the three thermoplastic polymers in the binder considered herein, High density polyethylene /Polypropylene performs better than the others in solvent debinding stage and in terms of the metal injection molding compact quality. High density polyethylene /Polypropylene has significantly better length, width and thickness by up to 46%, 40%, 20%, respectively. The density, hardness and tensile strength of the sintered parts are 7.28 g/cm3, 72.3 HRB and 579MPa.
A thorough of thermoplastic polymer in the wax-based binder is essential for ensuring the dimensions and mechanical properties of 316L stainless steel metal injection molding parts. The effects of three thermoplastic polymers, High density polyethylene, High density polyethylene /Polypropylene and Polypropylene, on the dimensions and mechanical properties of 316L stainless steel metal injection molding parts have been compared in this paper. The tensile bar is tested to examine the dimensions and mechanical properties of sintered parts against different thermoplastic polymers in the binder. Among the three thermoplastic polymers in the binder considered herein, High density polyethylene /Polypropylene performs better than the others in solvent debinding stage and in terms of the metal injection molding compact quality. High density polyethylene /Polypropylene has significantly better length, width and thickness by up to 46%, 40%, 20%, respectively. The density, hardness and tensile strength of the sintered parts are 7.28 g/cm3, 72.3 HRB and 579MPa.
2017, 46(10):2785-2789.
Abstract:
(La0.4Sm0.5Yb0.1)2Zr2O7 (LSYZO) coating was prepared by atmospheric plasma spray. Sm2Zr2O7 (SZO) coating was also prepared in the same conditions as a contrast. Microstructures and phases of LSYZO coatings were investigated by scanning electrical microscopy and X-ray diffraction, respectively. The thermal conductivities of the two coatings were measured. The results show that the phase composition of LSYZO coating has no change after plasma spraying. The adhesion strength of LSYZO coating is 22 MPa, which is comparable with that of SZO coating. And LSYZO coating has lifetime of about 40 cycles. The thermal conductivity of LSYZO coating is lower than that of SZO coating, which mainly depends on the complex structure of LSYZO ceramic.
(La0.4Sm0.5Yb0.1)2Zr2O7 (LSYZO) coating was prepared by atmospheric plasma spray. Sm2Zr2O7 (SZO) coating was also prepared in the same conditions as a contrast. Microstructures and phases of LSYZO coatings were investigated by scanning electrical microscopy and X-ray diffraction, respectively. The thermal conductivities of the two coatings were measured. The results show that the phase composition of LSYZO coating has no change after plasma spraying. The adhesion strength of LSYZO coating is 22 MPa, which is comparable with that of SZO coating. And LSYZO coating has lifetime of about 40 cycles. The thermal conductivity of LSYZO coating is lower than that of SZO coating, which mainly depends on the complex structure of LSYZO ceramic.
2017, 46(10):2790-2793.
Abstract:
A broad relaxation peak, which contributes to the high damping capacity around room temperature, has been obtained in all our investigated high damping magnesium alloys. This peak is a dislocation-related relaxation peak, which is probably caused by the interaction between dislocation and point defects (vacancy and solid atoms) during the dislocation movement on the basal plane actived by thermal. The grain boundary relaxation peak also has been observed in both Mg-Ni and Mg-0.6%Zr high damping alloys. However, it is necessary to point out that microstructure can affect the gain boundary relaxation. With Ni content increasing, the grain is refined and the grain boundary internal friction peak shifts to lower temperature. Compared with Mg-0.6%Zr alloy, the grain boundary internal friction peak shifts to higher temperature after adding a little yttrium(Y).
A broad relaxation peak, which contributes to the high damping capacity around room temperature, has been obtained in all our investigated high damping magnesium alloys. This peak is a dislocation-related relaxation peak, which is probably caused by the interaction between dislocation and point defects (vacancy and solid atoms) during the dislocation movement on the basal plane actived by thermal. The grain boundary relaxation peak also has been observed in both Mg-Ni and Mg-0.6%Zr high damping alloys. However, it is necessary to point out that microstructure can affect the gain boundary relaxation. With Ni content increasing, the grain is refined and the grain boundary internal friction peak shifts to lower temperature. Compared with Mg-0.6%Zr alloy, the grain boundary internal friction peak shifts to higher temperature after adding a little yttrium(Y).
2017, 46(10):2794-2800.
Abstract:
The model for single fiber push-out test is developed to evaluate the fracture toughness GIIc of the fiber/matrix interface in titanium alloys reinforced by SiC monofilaments. Theoretical solution to GIIc is obtained from fracture mechanics, and the effects of several key factors such as the applied stress needed for crack advance, crack length, and interfacial frictional shear stress are discussed. The predictions by the model are compared with the previous finite element analysis results for the interfacial toughness of the composites including Sigma1240/Ti-6-4, SCS/Ti-6-4, SCS/Timetal 834 and SCS/Timetal 21s. The results show that the model can reliably predict the interfacial toughness of the titanium matrix composites, in which interfacial debonding usually occurs at the bottom of the samples.
The model for single fiber push-out test is developed to evaluate the fracture toughness GIIc of the fiber/matrix interface in titanium alloys reinforced by SiC monofilaments. Theoretical solution to GIIc is obtained from fracture mechanics, and the effects of several key factors such as the applied stress needed for crack advance, crack length, and interfacial frictional shear stress are discussed. The predictions by the model are compared with the previous finite element analysis results for the interfacial toughness of the composites including Sigma1240/Ti-6-4, SCS/Ti-6-4, SCS/Timetal 834 and SCS/Timetal 21s. The results show that the model can reliably predict the interfacial toughness of the titanium matrix composites, in which interfacial debonding usually occurs at the bottom of the samples.
8 Study on the Effect of TiO2 Sol on the Microstructure and Tribological Properties of Cu-Sn Coating
2017, 46(10):2801-2806.
Abstract:
In order to improve the hardness and wear resistance, ensure the self-lubricating property, Cu-Sn coatings were prepared and strengthened by combining sol-gel method and composite electroplating technology. In the paper, TiO2 Sol was added to the Cu-Sn electroplating bath to obtain nano-particles enhanced Cu-Sn-TiO2 composite coatings. The micro-structure, microhardness and tribological properties were analyzed in detail. The results show that the introduction of the TiO2 Sol in the plating solution leads to change the composition and structure of the composite coatings. The co-deposited TiO2 is uniformly distributed in the Cu-Sn matrix and contributes greatly to improve the microhardness and tribological properties of the Cu-Sn alloy coating.
In order to improve the hardness and wear resistance, ensure the self-lubricating property, Cu-Sn coatings were prepared and strengthened by combining sol-gel method and composite electroplating technology. In the paper, TiO2 Sol was added to the Cu-Sn electroplating bath to obtain nano-particles enhanced Cu-Sn-TiO2 composite coatings. The micro-structure, microhardness and tribological properties were analyzed in detail. The results show that the introduction of the TiO2 Sol in the plating solution leads to change the composition and structure of the composite coatings. The co-deposited TiO2 is uniformly distributed in the Cu-Sn matrix and contributes greatly to improve the microhardness and tribological properties of the Cu-Sn alloy coating.
2017, 46(10):2807-2811.
Abstract:
Abstract: The hot corrosion resistance of CoCrAlSiY coating with different Si concentrations (0%, 2% and 5%) at 900 ℃ was discussed by using hot salt coating method with a mixed salt of 75wt% Na2SO4+25wt% NaCl. The CoCrAlSiY coating was prepared by HVOF method. The results show that the average corrosion penetration depth of coating increases with the rising temperature, while the increasing Si concentration decreases the average corrosion penetration depth of coating. Furthermore, CrSi, a high melting point metal silicide, is generated inside the CoCrAlSiY corrosion coating. Thus it is beneficial for improving the corrosion resistance of coating.
Abstract: The hot corrosion resistance of CoCrAlSiY coating with different Si concentrations (0%, 2% and 5%) at 900 ℃ was discussed by using hot salt coating method with a mixed salt of 75wt% Na2SO4+25wt% NaCl. The CoCrAlSiY coating was prepared by HVOF method. The results show that the average corrosion penetration depth of coating increases with the rising temperature, while the increasing Si concentration decreases the average corrosion penetration depth of coating. Furthermore, CrSi, a high melting point metal silicide, is generated inside the CoCrAlSiY corrosion coating. Thus it is beneficial for improving the corrosion resistance of coating.
10 Review on brazing of high volume faction SiCp/Al composites for electronic packaging applications
2017, 46(10):2812-2819.
Abstract:
High volume faction (HFC, ≥50%) SiCp/Al composites are becoming increasingly popular as the electronic packaging materials, and the brazing of them is therefore of great practical importance. Recently, some new filler metal alloys and processes have been developed for effectively brazing the HFC SiCp/Al composites. Starting from a survey of physical and mechanical properties and fabrication process of the HFC SiCp/Al composites, the filler metal, brazing process as well as the corresponding joint microstructures and strength are reviewed for understanding their relationships in order to improve the joining technique and joint reliability. The additions of Cu, Mg and Ni into Al?Si based alloy can contribute to improve the performances of filler metal and/or joint, such as the operating temperature of filler metal, interfacial bonding and brazing seam strength. Two assisted procedures involving surface metallization and ultrasonic vibration can better the brazability by avoiding or removing the inevitable oxide films (Al2O3 and SiO2) on the surface of HFC SiCp/Al composites. The need of further investigations, covering optimization design of filler metal, surface metallization process as well as wettability and interfacial behavior of filler-coating-SiCp/Al substrate system are strongly underlined.
High volume faction (HFC, ≥50%) SiCp/Al composites are becoming increasingly popular as the electronic packaging materials, and the brazing of them is therefore of great practical importance. Recently, some new filler metal alloys and processes have been developed for effectively brazing the HFC SiCp/Al composites. Starting from a survey of physical and mechanical properties and fabrication process of the HFC SiCp/Al composites, the filler metal, brazing process as well as the corresponding joint microstructures and strength are reviewed for understanding their relationships in order to improve the joining technique and joint reliability. The additions of Cu, Mg and Ni into Al?Si based alloy can contribute to improve the performances of filler metal and/or joint, such as the operating temperature of filler metal, interfacial bonding and brazing seam strength. Two assisted procedures involving surface metallization and ultrasonic vibration can better the brazability by avoiding or removing the inevitable oxide films (Al2O3 and SiO2) on the surface of HFC SiCp/Al composites. The need of further investigations, covering optimization design of filler metal, surface metallization process as well as wettability and interfacial behavior of filler-coating-SiCp/Al substrate system are strongly underlined.
2017, 46(10):2820-2824.
Abstract:
WC–Ni composite powders have been prepared by electroless plating with a simplified chemical method. The original WC powders, pretreated WC powders, WC–Ni powders and surface of WC–Ni composites, as well as their fracture cross-sections, were analyzed by FESEM. EDS and XRD were performed to identify the composition. Different contents of Ni doping WC composites were investigated. The relative density and properties of the WC–Ni composite were also discussed. Results show the WC powders were uniformly covered by Ni coatings. After powder metallurgy, the fabricated composites performed a well-dispersed surface morphology. And the increasing Ni content enhanced bending strength without reducing excessive hardness, which involved the uniformity of Ni phase in the crystal boundary of WC. Trans-granular fractures were observed on the surface of the WC–Ni composite because of the uniformity of binder phase (Ni).
WC–Ni composite powders have been prepared by electroless plating with a simplified chemical method. The original WC powders, pretreated WC powders, WC–Ni powders and surface of WC–Ni composites, as well as their fracture cross-sections, were analyzed by FESEM. EDS and XRD were performed to identify the composition. Different contents of Ni doping WC composites were investigated. The relative density and properties of the WC–Ni composite were also discussed. Results show the WC powders were uniformly covered by Ni coatings. After powder metallurgy, the fabricated composites performed a well-dispersed surface morphology. And the increasing Ni content enhanced bending strength without reducing excessive hardness, which involved the uniformity of Ni phase in the crystal boundary of WC. Trans-granular fractures were observed on the surface of the WC–Ni composite because of the uniformity of binder phase (Ni).
12 Mechanical behavior and microstructure evolution of Al-Cu-Li alloy during multi-pass hot deformation
Yang Shengli
,
Shen Jian
,
Li Xiwu
,
Yan Xiaodong
,
Zhang Yongan
,
Li Zhihui
,
Huang Shuhui
,
Xiong Baiqing
2017, 46(10):2825-2830.
Abstract:
Continuous, discontinuous, double-pass and multi-pass hot isothermal compression tests were conducted to understand the mechanical behavior and microstructure evolution of the Al-2.5wt%Cu-1.58wt%Li-0.3wt%Mn-0.12wt%Zr-0.06wt%Mg-0.05 wt%Ti alloy. The tests were conducted in the temperature of 420℃ and at strain rates of 0.001, 0.1 and 10s-1 on Gleeble-1500. EBSD and TEM were used to investigate microstructure evolution at different deformation stages of the alloy. Double-pass hot deformation results show that the extension of interval time between two passes is conductive to promoting static softening. It is possible to control the grain size in the test alloy by changing the strain rate at different deformation stage. During multi-pass hot deformation process, static softening between the deformation pass is beneficial to the dynamic softening, vice versa. Dynamic precipitation of T1 and θ′ phase is observed during the multi-pass deformation process(T=420℃, =0.1s-1). In the initial stage of multi-pass deformation, strain-induced dislocations provide the nucleation site for θ′ and T1 phase, promoting their precipitation and coarsening. With increasing of strain, the size of the precipitates T1 and θ′ phase decreased and then tend to be stable, the density of δ′ phase decreased. Flow stress of the test alloy during multi-pass hot deformation is influenced by dynamic softening, static softening and dynamic precipitation.
Continuous, discontinuous, double-pass and multi-pass hot isothermal compression tests were conducted to understand the mechanical behavior and microstructure evolution of the Al-2.5wt%Cu-1.58wt%Li-0.3wt%Mn-0.12wt%Zr-0.06wt%Mg-0.05 wt%Ti alloy. The tests were conducted in the temperature of 420℃ and at strain rates of 0.001, 0.1 and 10s-1 on Gleeble-1500. EBSD and TEM were used to investigate microstructure evolution at different deformation stages of the alloy. Double-pass hot deformation results show that the extension of interval time between two passes is conductive to promoting static softening. It is possible to control the grain size in the test alloy by changing the strain rate at different deformation stage. During multi-pass hot deformation process, static softening between the deformation pass is beneficial to the dynamic softening, vice versa. Dynamic precipitation of T1 and θ′ phase is observed during the multi-pass deformation process(T=420℃, =0.1s-1). In the initial stage of multi-pass deformation, strain-induced dislocations provide the nucleation site for θ′ and T1 phase, promoting their precipitation and coarsening. With increasing of strain, the size of the precipitates T1 and θ′ phase decreased and then tend to be stable, the density of δ′ phase decreased. Flow stress of the test alloy during multi-pass hot deformation is influenced by dynamic softening, static softening and dynamic precipitation.
2017, 46(10):2837-2841.
Abstract:
In this study, the alumina coatings as tritium permeation barrier were successfully prepared on stainless steel bulk by composite low temperature plasma method of magnetron sputtering, heat treatment and O ion implantation. The phases, surface morphologies, chemical composition and O distribution of the coatings were characterized by XRD, SEM, EDS and AES individually,and after analyzing through scratch adhesion test, thermal shock resistance test and tritium permeability test. The results show that the Al coatings deposited by magnetron sputtering is well, and Fe-Al alloys interlayer was formed after heat treatment. In O ion implantation process, the oxygen depth deepened and the oxygen density gradient decreased with higher accelerating voltage at definite doses, meanwhile it can be seen that 8×1017 ions/cm2 is the crucial dose, above which ion implantation the oxygen density was more homogeneous. After a series tests, the obtained coatings has the good performance with film-substrate cohesion, thermal shock resistance and the tritium permeation resistance, and the coatings, which were treated by superposition at 8×1017 ions/cm2doses, have the best tritium permeability resistance, and it was improved 3 orders of magnitude high than the stainless steel bulk.
In this study, the alumina coatings as tritium permeation barrier were successfully prepared on stainless steel bulk by composite low temperature plasma method of magnetron sputtering, heat treatment and O ion implantation. The phases, surface morphologies, chemical composition and O distribution of the coatings were characterized by XRD, SEM, EDS and AES individually,and after analyzing through scratch adhesion test, thermal shock resistance test and tritium permeability test. The results show that the Al coatings deposited by magnetron sputtering is well, and Fe-Al alloys interlayer was formed after heat treatment. In O ion implantation process, the oxygen depth deepened and the oxygen density gradient decreased with higher accelerating voltage at definite doses, meanwhile it can be seen that 8×1017 ions/cm2 is the crucial dose, above which ion implantation the oxygen density was more homogeneous. After a series tests, the obtained coatings has the good performance with film-substrate cohesion, thermal shock resistance and the tritium permeation resistance, and the coatings, which were treated by superposition at 8×1017 ions/cm2doses, have the best tritium permeability resistance, and it was improved 3 orders of magnitude high than the stainless steel bulk.
2017, 46(10):2842-2846.
Abstract:
This paper focuses on the numerical simulation of non-equal sintering metal powers by surface diffusion. In order to simulate the sintering process of non-equal metal powders clearly, the surface diffusion model is modified by establishing more suitable initial boundary conditions. And this model is numerically solved by the finite difference method. The three-dimensional numerical simulations of two metal powers with radii ratios 1:1, 1:1.5, 1:2 are implemented by this model. Through comparison, the simulation results are consistent with the experimental ones. Finally, the effect of metal powders’ radii ratios on the growth rate of sintering neck is investigated, which implies that the sintering neck radius increases with the decreasing of radii ratios.
This paper focuses on the numerical simulation of non-equal sintering metal powers by surface diffusion. In order to simulate the sintering process of non-equal metal powders clearly, the surface diffusion model is modified by establishing more suitable initial boundary conditions. And this model is numerically solved by the finite difference method. The three-dimensional numerical simulations of two metal powers with radii ratios 1:1, 1:1.5, 1:2 are implemented by this model. Through comparison, the simulation results are consistent with the experimental ones. Finally, the effect of metal powders’ radii ratios on the growth rate of sintering neck is investigated, which implies that the sintering neck radius increases with the decreasing of radii ratios.
2017, 46(10):2847-2851.
Abstract:
1wt% SiC nanoparticles reinforced Mg-9Al-1Zn magnesium matrix composite was fabricated by stir casting and hot extrusion. Effect of stirring for 10min and 30min respectively on microstructure and mechanical properties of SiCp/Mg-9Al-1Zn nanocomposite was researched. The results show that the grains of the matrix in the as-cast SiCp/Mg-9Al-1Zn nanocomposite stirring for 30min are mainly refined. But the mechanical properties of nanocomposite decline due to the increase of agglomerated SiC nanoparticles and Mg17Al12 phases with network morphology along the grain boundaries. After hot extrusion, a bimodal microstructure composed of alternate arrays of fine DRXed grains and relatively coarse DRXed grains is formed. Particularly, for as-extrusion nanocomposites stirring for 30min, the fine DRXed region can be increased and the distribution of SiC nanoparticles is more homogenous, which can exhibit superior mechanical properties compared with as-extruded SiCp/Mg-9Al-1Zn nanocomposite stirring for 10min.
1wt% SiC nanoparticles reinforced Mg-9Al-1Zn magnesium matrix composite was fabricated by stir casting and hot extrusion. Effect of stirring for 10min and 30min respectively on microstructure and mechanical properties of SiCp/Mg-9Al-1Zn nanocomposite was researched. The results show that the grains of the matrix in the as-cast SiCp/Mg-9Al-1Zn nanocomposite stirring for 30min are mainly refined. But the mechanical properties of nanocomposite decline due to the increase of agglomerated SiC nanoparticles and Mg17Al12 phases with network morphology along the grain boundaries. After hot extrusion, a bimodal microstructure composed of alternate arrays of fine DRXed grains and relatively coarse DRXed grains is formed. Particularly, for as-extrusion nanocomposites stirring for 30min, the fine DRXed region can be increased and the distribution of SiC nanoparticles is more homogenous, which can exhibit superior mechanical properties compared with as-extruded SiCp/Mg-9Al-1Zn nanocomposite stirring for 10min.
2017, 46(10):2852-2856.
Abstract:
The evolution of primary α phase morphology and mechanical properties of a new high-strength titanium alloy during heat treatment were investigated. The results show that the primary α phases tend to globular growth feature on the basis of the equiaxed α phases underα/β zone double solution treatment at air cooling process. But abnormal growth of primary α grains occurs in the 0.5℃/minfurnace cooling processwhich except some primary alpha remains spherical growth, another parts evolve similar “fork” shapeddendritic growth rather than keep nearly spherical growth trend. The new titanium alloy leads to attractive combinations of strength and ductility (≈1300MPa of ultimate strength with 10.5% of elongation) at the microstructures obtained a few equiaxed or thin billet-like primary α phase and fine lamellar secondary α phase under α/β solution treatment followed by air cooling plus aging.The new alloyafter α/β solution treatment followed furnace cooling to low temperature and then aging heat treatment process has an excellent values (≥80 MPa?m1/2). Meanwhile, the elongation and reduction ofarea remain at about 19% and 45% respectively, and its corresponding tensile strength maintains at about1000 MPa.It can be assumed that the alloy may be a usable structural material.
The evolution of primary α phase morphology and mechanical properties of a new high-strength titanium alloy during heat treatment were investigated. The results show that the primary α phases tend to globular growth feature on the basis of the equiaxed α phases underα/β zone double solution treatment at air cooling process. But abnormal growth of primary α grains occurs in the 0.5℃/minfurnace cooling processwhich except some primary alpha remains spherical growth, another parts evolve similar “fork” shapeddendritic growth rather than keep nearly spherical growth trend. The new titanium alloy leads to attractive combinations of strength and ductility (≈1300MPa of ultimate strength with 10.5% of elongation) at the microstructures obtained a few equiaxed or thin billet-like primary α phase and fine lamellar secondary α phase under α/β solution treatment followed by air cooling plus aging.The new alloyafter α/β solution treatment followed furnace cooling to low temperature and then aging heat treatment process has an excellent values (≥80 MPa?m1/2). Meanwhile, the elongation and reduction ofarea remain at about 19% and 45% respectively, and its corresponding tensile strength maintains at about1000 MPa.It can be assumed that the alloy may be a usable structural material.
2017, 46(10):2857-2862.
Abstract:
During the last past decades, TiN/CrN muiltilayer coatings have been extensively developed to improve the performance and lifetime of components due to their excellent mechanical properties. In order to study the relationship between mechanical properties and microstructure of TiN/CrN multilayer coatings, the TiN, CrN film and threeTiN/CrN multilayer films with different periodicities were prepared on monocrystalline silicon by magnetron sputtering. Atomic Force Microscope and X-ray diffraction were adopted to analyse the surface morphology and chemical construction of the films. The hardness and indentation plasticity were studied using nanoindenter. Residual stress was measured by curvature method. The results show that TiN/CrN multilayer films exhibit a mixture of TiN and Cr2N phases, the interface zone between TiN layer and CrN layer become small and sharp with the increasing of periodicity. Hardness and indentation plasticity of multilayer films are better than monolayer films, and increase as the bilayer period decreases. For multilayer films, the residual stress increases gradually with the increasing of periodicity. From the above observation, it can be concluded that the improvement in mechanical property depend on minor periodicity. The results agree well with Hall–Petch theory.
During the last past decades, TiN/CrN muiltilayer coatings have been extensively developed to improve the performance and lifetime of components due to their excellent mechanical properties. In order to study the relationship between mechanical properties and microstructure of TiN/CrN multilayer coatings, the TiN, CrN film and threeTiN/CrN multilayer films with different periodicities were prepared on monocrystalline silicon by magnetron sputtering. Atomic Force Microscope and X-ray diffraction were adopted to analyse the surface morphology and chemical construction of the films. The hardness and indentation plasticity were studied using nanoindenter. Residual stress was measured by curvature method. The results show that TiN/CrN multilayer films exhibit a mixture of TiN and Cr2N phases, the interface zone between TiN layer and CrN layer become small and sharp with the increasing of periodicity. Hardness and indentation plasticity of multilayer films are better than monolayer films, and increase as the bilayer period decreases. For multilayer films, the residual stress increases gradually with the increasing of periodicity. From the above observation, it can be concluded that the improvement in mechanical property depend on minor periodicity. The results agree well with Hall–Petch theory.
2017, 46(10):2863-2869.
Abstract:
The preferred site of Cr or Mo alloying element in the DO3-Fe3Al intermetallic compounds, and the effect of Cr or Mo on the mechanical properties and electronic structure of Fe3Al are investigated by first-principle based on density functional theory. The research demonstrated that Cr or Mo preferred substitutes the Al atom in Fe3Al, and Cr or Mo increases the bulk moduli, rigidity moduli and Young"s modulus of Fe3Al and improves the ductility of Fe3Al. According to the analysis of the electronic structure and the electronic density, the effect on improving the mechanical properties of Fe3Al can be mainly attributed to the s, p, d-state orbital electron of the element Cr or Mo dropped is involved in hybridization of Fe3Al, Cr or Mo has increased the number of the bonding peaks of Fe3Al and overlapping electron number among atoms of Fe3Al, in addition, Cr or Mo decrease the directionality of electron atmosphere between Fe-Fe of Fe3Al.
The preferred site of Cr or Mo alloying element in the DO3-Fe3Al intermetallic compounds, and the effect of Cr or Mo on the mechanical properties and electronic structure of Fe3Al are investigated by first-principle based on density functional theory. The research demonstrated that Cr or Mo preferred substitutes the Al atom in Fe3Al, and Cr or Mo increases the bulk moduli, rigidity moduli and Young"s modulus of Fe3Al and improves the ductility of Fe3Al. According to the analysis of the electronic structure and the electronic density, the effect on improving the mechanical properties of Fe3Al can be mainly attributed to the s, p, d-state orbital electron of the element Cr or Mo dropped is involved in hybridization of Fe3Al, Cr or Mo has increased the number of the bonding peaks of Fe3Al and overlapping electron number among atoms of Fe3Al, in addition, Cr or Mo decrease the directionality of electron atmosphere between Fe-Fe of Fe3Al.
2017, 46(10):2870-2876.
Abstract:
Prepared Al-15wt.%Mg2Si composite by in-situ, little research had been done in binary phase of Al-15wt.%Mg2Si composite. Employed the method of qualitative and quantitative analysis to confirm the phase components and content by XRD test. Simulated the XRD Patten of Al-Mg-Si alloy by Reflex and compared the simulated result with testing result. Lattice constants, thermodynamic parameter and elastic constant of Mg2Si phase and Mg17Al12 phase in Al-Mg2Si composite were investigated by means of first-principle calculations from CASTEP program based on density functional theory, in order to compare the stability and mechanical properties. There are only α-Al phase and Mg2Si phase in Al-15wt.%Mg2Si composite shown in XRD testing result; and the mass fraction of phase Mg2Si is 14.9%. The differences of XRD indices with same crystal plane (h k l) between simulation and test is fractional. Therefore, the simulated result by reflex is reliable. Only α-Al phase and Mg2Si phase are formed in theory shown by simulation. The calculated heats of formation and cohesive energies show that Mg2Si phase is easy to form and the alloying ability is more strong. Mg2Si phase is more stable than Mg17Al12 phase. Elastic modulus (E), shear modulus (G), bulk modulus (B) of Mg2Si phase is better than Mg17Al12 phase. However, the friability of Mg2Si phase is better and the plasticity is lower.
Prepared Al-15wt.%Mg2Si composite by in-situ, little research had been done in binary phase of Al-15wt.%Mg2Si composite. Employed the method of qualitative and quantitative analysis to confirm the phase components and content by XRD test. Simulated the XRD Patten of Al-Mg-Si alloy by Reflex and compared the simulated result with testing result. Lattice constants, thermodynamic parameter and elastic constant of Mg2Si phase and Mg17Al12 phase in Al-Mg2Si composite were investigated by means of first-principle calculations from CASTEP program based on density functional theory, in order to compare the stability and mechanical properties. There are only α-Al phase and Mg2Si phase in Al-15wt.%Mg2Si composite shown in XRD testing result; and the mass fraction of phase Mg2Si is 14.9%. The differences of XRD indices with same crystal plane (h k l) between simulation and test is fractional. Therefore, the simulated result by reflex is reliable. Only α-Al phase and Mg2Si phase are formed in theory shown by simulation. The calculated heats of formation and cohesive energies show that Mg2Si phase is easy to form and the alloying ability is more strong. Mg2Si phase is more stable than Mg17Al12 phase. Elastic modulus (E), shear modulus (G), bulk modulus (B) of Mg2Si phase is better than Mg17Al12 phase. However, the friability of Mg2Si phase is better and the plasticity is lower.
Zhang Min
,
Luo Wenbin
,
Ding Jiating
,
Cheng Hongmei
,
Ouyang Yifang
,
Yuan Gaihuan
,
Zhu Jinming
,
Liang Jianlie
2017, 46(10):2877-2882.
Abstract:
The isothermal section of the Zr-Fe-Cu ternary system at 700 ℃ was investigated by using X-ray diffraction, Scanning Electron Microscope and Energy Disperse Analysis. Two Zr-Fe-Cu ternary phase, Zr(Fe,Cu) and Zr2(Fe,Cu), named τ1 and τ2, have been found in this section. Nine binary phases, Fe2Zr, FeZr3, CuZr2, Cu10Zr7, Cu8Zr3, Cu51Zr14 and Cu5Zr, were confirmed to be stable at this temperature. Large amount of Fe (18.6 at.%) was observed to solute in Cu51Zr14. In addition, the oxygen stabililized phase Fe23Zr6 wasn’t observed in Zr-Fe-Cu ternary system.
The isothermal section of the Zr-Fe-Cu ternary system at 700 ℃ was investigated by using X-ray diffraction, Scanning Electron Microscope and Energy Disperse Analysis. Two Zr-Fe-Cu ternary phase, Zr(Fe,Cu) and Zr2(Fe,Cu), named τ1 and τ2, have been found in this section. Nine binary phases, Fe2Zr, FeZr3, CuZr2, Cu10Zr7, Cu8Zr3, Cu51Zr14 and Cu5Zr, were confirmed to be stable at this temperature. Large amount of Fe (18.6 at.%) was observed to solute in Cu51Zr14. In addition, the oxygen stabililized phase Fe23Zr6 wasn’t observed in Zr-Fe-Cu ternary system.
2017, 46(10):2883-2888.
Abstract:
Traditionally, the fracture toughness (K1C) of porous ceramics is evaluated by single edge notched beam method (SENB). For porous ceramics, the fracture toughness by SENB increases with decreasing porosity, it demonstrating that lower porosity improve the crack propagation resistance. However, previous experimental experience suggests that the thermal shock damage resistance (R"""") of porous ceramics will be increased with increasing porosity, it demonstrating that the high-porosity ceramics have the better capability to improve the crack propagation resistance in thermal shock situation. It is obvious that the SENB method is concluded to be in contradiction with the thermal shock damage theory. The uniaxial compression testing of porous ceramic indicating that the σ-ε curve can be divided into two parts, linear part and nonlinear part. Due to the metastable propagation of multi-micro-crack, the σ-ε curve displays nonlinear behavior. The fracture energy measured by uniaxial compression testing can be also used to characterize the quantity of mirco-crack-toughen effect, it can improve the test method of fracture toughness for porous ceramics.
Traditionally, the fracture toughness (K1C) of porous ceramics is evaluated by single edge notched beam method (SENB). For porous ceramics, the fracture toughness by SENB increases with decreasing porosity, it demonstrating that lower porosity improve the crack propagation resistance. However, previous experimental experience suggests that the thermal shock damage resistance (R"""") of porous ceramics will be increased with increasing porosity, it demonstrating that the high-porosity ceramics have the better capability to improve the crack propagation resistance in thermal shock situation. It is obvious that the SENB method is concluded to be in contradiction with the thermal shock damage theory. The uniaxial compression testing of porous ceramic indicating that the σ-ε curve can be divided into two parts, linear part and nonlinear part. Due to the metastable propagation of multi-micro-crack, the σ-ε curve displays nonlinear behavior. The fracture energy measured by uniaxial compression testing can be also used to characterize the quantity of mirco-crack-toughen effect, it can improve the test method of fracture toughness for porous ceramics.
2017, 46(10):2889-2894.
Abstract:
It has been attracted increasing interest and attention of researchers and engineers that the trace rare lanthanum and cerium addition increased the proportion of the equiaxed grains and led to grain refinement in solidified microstructure of steels. Generally, it was considered that such grain refinement was attributed to the heterogeneous nucleation of the high-melting-point rare earth inclusions when the rare earth elements exist in the form of inclusions in steel. The inconsistent previously reported results drives the in-depth study of the grain refining efficiency of these inclusions for steel castings. In the present work, the edge-to-edge matching model was used to calculate the atomic matching between the RE inclusions, namely Ce2O3 and La2O3, and the primary phase (both δ-Fe and γ-Fe), in order to predict the possibility and the potency of RE2O3 acting as the heterogeneous nucleation sites in liquid steel and also provide fresh insight into the understanding of the grain refinement mechanism of rare earth in the solidification of steels from the point of view of crystallography. The results show that both Ce2O3 and La2O3 are potent nucleant for heterogeneous nucleation of both δ-Fe and γ-Fe primary phases during solidification of steels. But, the grain refining potency of Ce2O3 and La2O3 for δ-Fe is higher than that for γ-Fe. Moreover, for γ-Fe, the La2O3 is more efficient than Ce2O3.
It has been attracted increasing interest and attention of researchers and engineers that the trace rare lanthanum and cerium addition increased the proportion of the equiaxed grains and led to grain refinement in solidified microstructure of steels. Generally, it was considered that such grain refinement was attributed to the heterogeneous nucleation of the high-melting-point rare earth inclusions when the rare earth elements exist in the form of inclusions in steel. The inconsistent previously reported results drives the in-depth study of the grain refining efficiency of these inclusions for steel castings. In the present work, the edge-to-edge matching model was used to calculate the atomic matching between the RE inclusions, namely Ce2O3 and La2O3, and the primary phase (both δ-Fe and γ-Fe), in order to predict the possibility and the potency of RE2O3 acting as the heterogeneous nucleation sites in liquid steel and also provide fresh insight into the understanding of the grain refinement mechanism of rare earth in the solidification of steels from the point of view of crystallography. The results show that both Ce2O3 and La2O3 are potent nucleant for heterogeneous nucleation of both δ-Fe and γ-Fe primary phases during solidification of steels. But, the grain refining potency of Ce2O3 and La2O3 for δ-Fe is higher than that for γ-Fe. Moreover, for γ-Fe, the La2O3 is more efficient than Ce2O3.
2017, 46(10):2895-2899.
Abstract:
The microstructure evolution and the change of Burgers orientation relationship between α and β phase of TC17 titanium alloy with initial lamellar microstructure were analyzed and researched by EBSD. The results shown that dynamic recrystallization of β phase was occured during hot deformation process. Meanwhile, the dynamic globularization of α phase contained the formation of subboundary and the fragmentation of α phase. The fragmentized α phase was eventually transformed to globularized particle. Meanwhile, the strict Burgers orientation relationship between α and β phase was destroyed, which was due to the activation of prismatic slip system and othe slip or twin system.
The microstructure evolution and the change of Burgers orientation relationship between α and β phase of TC17 titanium alloy with initial lamellar microstructure were analyzed and researched by EBSD. The results shown that dynamic recrystallization of β phase was occured during hot deformation process. Meanwhile, the dynamic globularization of α phase contained the formation of subboundary and the fragmentation of α phase. The fragmentized α phase was eventually transformed to globularized particle. Meanwhile, the strict Burgers orientation relationship between α and β phase was destroyed, which was due to the activation of prismatic slip system and othe slip or twin system.
2017, 46(10):2900-2907.
Abstract:
The Radial Forging Combined with Unidirectional Compression Recrystallization and Partial Melt (RFCUC-RAP) and Radial Forging Combined with Multi-axial Compression Recrystallization and Partial Melt (RFCMC-RAP) were proposed to prepared semi-solid billet. The microstructural evolutions of semi-solid 6063 Al alloy prepared by direct semi-solid isothermal treatment (SSIT), RFCUC-RAP and RFCMC-RAP were investigated. Results show that, the solid grains of semi-solid billet prepared by direct SSIT are large. However, solid grains of semi-solid billet prepared by RFCUC-RAP and RFCMC-RAP are fine and spherical. Additionally, the RFCUC-RAP is superior to the RFCMC-RAP owing to the relatively simple deformation process, which is an effective method to prepare high-quality semi-solid billet.
The Radial Forging Combined with Unidirectional Compression Recrystallization and Partial Melt (RFCUC-RAP) and Radial Forging Combined with Multi-axial Compression Recrystallization and Partial Melt (RFCMC-RAP) were proposed to prepared semi-solid billet. The microstructural evolutions of semi-solid 6063 Al alloy prepared by direct semi-solid isothermal treatment (SSIT), RFCUC-RAP and RFCMC-RAP were investigated. Results show that, the solid grains of semi-solid billet prepared by direct SSIT are large. However, solid grains of semi-solid billet prepared by RFCUC-RAP and RFCMC-RAP are fine and spherical. Additionally, the RFCUC-RAP is superior to the RFCMC-RAP owing to the relatively simple deformation process, which is an effective method to prepare high-quality semi-solid billet.
2017, 46(10):2908-2914.
Abstract:
The present paper describes a new technology to manufacture nanocrystalline materials of ZK60 alloys via studying the influence of hydride temperature, hydrogen pressure and reaction time of the HDDR process on the course of hydrogen-desorption, By the means of XRD, OM, SEM and TEM technique, the microstructural evolution of magnesium alloy was researched. Experimental results show that the temperature plays an important role in the hydrogen-desorption process of ZK60 alloy. In the optimal HD process for preparing nanocrystalline Mg alloy powders is that the alloy is hydrogenated at temperature of 350℃ under 2MPa hydrogen pressure for 12 hours and then dehydrogenated at 350℃ for 3 hours in vacuum. As a result, the grain sizes of ZK60 alloy were refined to about 20nm from 160mm.
The present paper describes a new technology to manufacture nanocrystalline materials of ZK60 alloys via studying the influence of hydride temperature, hydrogen pressure and reaction time of the HDDR process on the course of hydrogen-desorption, By the means of XRD, OM, SEM and TEM technique, the microstructural evolution of magnesium alloy was researched. Experimental results show that the temperature plays an important role in the hydrogen-desorption process of ZK60 alloy. In the optimal HD process for preparing nanocrystalline Mg alloy powders is that the alloy is hydrogenated at temperature of 350℃ under 2MPa hydrogen pressure for 12 hours and then dehydrogenated at 350℃ for 3 hours in vacuum. As a result, the grain sizes of ZK60 alloy were refined to about 20nm from 160mm.
2017, 46(10):2915-2921.
Abstract:
The fatigue crack growth rate of difficult-to-deform superalloy GH4720Li are investigated at 650℃, 700℃, 750℃and 800℃. The analysis of temperature effect on fatigue crack growth rate under pure fatigue and fatigue with 90s dwell. The result shows that the fatigue crack growth rate(FCGR) and increasing rate increased as the temperature increased. FCGR increase rapidly at 800℃. Temperature changes the model of the fatigue crack propagation, the fracture mode is the mix of transgranular and intergranular at 650℃, the fracture mode is predominantly inergranular at 700~800℃. The crack growth rate increased significantly with increasing the holding time. The higher test temperature is, the greater effect of dwell time on crack growth rate.
The fatigue crack growth rate of difficult-to-deform superalloy GH4720Li are investigated at 650℃, 700℃, 750℃and 800℃. The analysis of temperature effect on fatigue crack growth rate under pure fatigue and fatigue with 90s dwell. The result shows that the fatigue crack growth rate(FCGR) and increasing rate increased as the temperature increased. FCGR increase rapidly at 800℃. Temperature changes the model of the fatigue crack propagation, the fracture mode is the mix of transgranular and intergranular at 650℃, the fracture mode is predominantly inergranular at 700~800℃. The crack growth rate increased significantly with increasing the holding time. The higher test temperature is, the greater effect of dwell time on crack growth rate.
2017, 46(10):2922-2928.
Abstract:
In order to provide theoretical guidance for production process contorl and performance optimization, the microstructure evolution and heat treatment process in the production procecss of GH5188 cobalt-base superalloy were investigated by SEM, EDS and Thermo-Calc software. The result indicates that the main phases of GH5188 alloy include γ, M6C and M23C6. The 1200°C/20h could reduce segregation of as-cast microstructure. Hot-rolled microstructure have a fine grain size, and a large number of aligned carbides precipitate along rolling direction. In the cold-rolled microstructure with serious grain deformation, granular M6C was found to be predominant phase. when the annealing temperature is higher than 1170°C, secondary carbides at the grain boundaries dissolved back into γ and recrystallized grain can grow in normal way.
In order to provide theoretical guidance for production process contorl and performance optimization, the microstructure evolution and heat treatment process in the production procecss of GH5188 cobalt-base superalloy were investigated by SEM, EDS and Thermo-Calc software. The result indicates that the main phases of GH5188 alloy include γ, M6C and M23C6. The 1200°C/20h could reduce segregation of as-cast microstructure. Hot-rolled microstructure have a fine grain size, and a large number of aligned carbides precipitate along rolling direction. In the cold-rolled microstructure with serious grain deformation, granular M6C was found to be predominant phase. when the annealing temperature is higher than 1170°C, secondary carbides at the grain boundaries dissolved back into γ and recrystallized grain can grow in normal way.
2017, 46(10):2929-2935.
Abstract:
The influence of the dissolution process of γ'' phase on the subsequent precipitating process of γ'' phase was investigated and the effect of Al+Ti contents and Ti/Al ratios to γ'' precipitate was also simulated. The precipitation of γ'' phase are influenced by the dissolution of γ'' phase and the diffusion of Al and Ti content. The size of γ'' precipitate decreases with the increase of solution time and temperature. The precipitation of γ'' phase exhibits various sizes, shapes and distributions under the water cooling condition. It can be shown in TTT and CCT curves that the precipitating temperature increases and the precipitating time decreases under various cooling rates with changes in Al+Ti contents. The precipitation of γ'' phase can not inhibited under the water cooling condition and even when the cooling rate is 1000 ℃/min. Meanwhile, no obvious influence is observed on the precipitation process of γ'' phase with the various Ti/Al ratios.
The influence of the dissolution process of γ'' phase on the subsequent precipitating process of γ'' phase was investigated and the effect of Al+Ti contents and Ti/Al ratios to γ'' precipitate was also simulated. The precipitation of γ'' phase are influenced by the dissolution of γ'' phase and the diffusion of Al and Ti content. The size of γ'' precipitate decreases with the increase of solution time and temperature. The precipitation of γ'' phase exhibits various sizes, shapes and distributions under the water cooling condition. It can be shown in TTT and CCT curves that the precipitating temperature increases and the precipitating time decreases under various cooling rates with changes in Al+Ti contents. The precipitation of γ'' phase can not inhibited under the water cooling condition and even when the cooling rate is 1000 ℃/min. Meanwhile, no obvious influence is observed on the precipitation process of γ'' phase with the various Ti/Al ratios.
2017, 46(10):2936-2942.
Abstract:
The high temperature hot compressive deformation behavior of as-cast ZK60-1.0Er magnesium alloy occurring homogenization have been studied by Gleeble-1500D thermal simulator at the strain rate 0.0001s-1,0.001s-1,0.01s-1 and 1.0s-1,the temperature 160℃, 260℃, 320℃ and 420℃. The experimental results show that the competition between work hardening, dynamic recovery and dynamic recrystallization of hot compression deformation of as-cast ZK60-1.0Er magnesium alloy. Constitutive equation of thermocompression of ZK60-1.0Er magnesium alloy was developed by the Zener-Hollomon parameter, theorial stress value which was calculated according to the constitutive equation is in accordance with the actual stress value; Meanwhile according to the material dynamic model, the processing map of this magnesium alloy was obtained, in addition, observing and analyzing metallographic microstructure shows that the processing map contains two instability areas: low temperature high strain rate and high temperature low strain rate. The most optimal hot working range for this kind of alloy: 225~420℃, 0.01~1.0s-1, having one peak efficiency η max = 45%. The existence of rare earth promote dynamic recrystallization nucleation of ZK60-1.0Er magnesium alloy, the average deformation activation energy was 152.5KJ/mol, main mechanisms were dynamic recovery and dynamic recrystallization caused by the grain boundary sliding and lattice self-diffusion.
The high temperature hot compressive deformation behavior of as-cast ZK60-1.0Er magnesium alloy occurring homogenization have been studied by Gleeble-1500D thermal simulator at the strain rate 0.0001s-1,0.001s-1,0.01s-1 and 1.0s-1,the temperature 160℃, 260℃, 320℃ and 420℃. The experimental results show that the competition between work hardening, dynamic recovery and dynamic recrystallization of hot compression deformation of as-cast ZK60-1.0Er magnesium alloy. Constitutive equation of thermocompression of ZK60-1.0Er magnesium alloy was developed by the Zener-Hollomon parameter, theorial stress value which was calculated according to the constitutive equation is in accordance with the actual stress value; Meanwhile according to the material dynamic model, the processing map of this magnesium alloy was obtained, in addition, observing and analyzing metallographic microstructure shows that the processing map contains two instability areas: low temperature high strain rate and high temperature low strain rate. The most optimal hot working range for this kind of alloy: 225~420℃, 0.01~1.0s-1, having one peak efficiency η max = 45%. The existence of rare earth promote dynamic recrystallization nucleation of ZK60-1.0Er magnesium alloy, the average deformation activation energy was 152.5KJ/mol, main mechanisms were dynamic recovery and dynamic recrystallization caused by the grain boundary sliding and lattice self-diffusion.
2017, 46(10):2943-2949.
Abstract:
A layer of W skeleton with 100-200μm was obtained by corroding the Cu of CuW surface. Then, a porous structure diffusion barrier layer was formed by electroless Ni plating on W skeleton. Finally, the CuW/Al bimetals was prepared by using solid-liquid connection at 700℃. The microstructure of interfacial diffusion layer at different holding time was investigated, and the precipitation sequence of the intermetallic compounds was analyzed. The results show that the porous structure Ni interlayer between CuW/Al interface can effectively reduce the amount of Al2Cu compounds, and prevent the formation of Kirkendall voids. The CuW/Al interface mainly consists of Al2Cu and Al5W phases. By adding porous structure Ni interlayer, the interface bonding property and electrical conductivity of CuW/Al were improved.
A layer of W skeleton with 100-200μm was obtained by corroding the Cu of CuW surface. Then, a porous structure diffusion barrier layer was formed by electroless Ni plating on W skeleton. Finally, the CuW/Al bimetals was prepared by using solid-liquid connection at 700℃. The microstructure of interfacial diffusion layer at different holding time was investigated, and the precipitation sequence of the intermetallic compounds was analyzed. The results show that the porous structure Ni interlayer between CuW/Al interface can effectively reduce the amount of Al2Cu compounds, and prevent the formation of Kirkendall voids. The CuW/Al interface mainly consists of Al2Cu and Al5W phases. By adding porous structure Ni interlayer, the interface bonding property and electrical conductivity of CuW/Al were improved.
2017, 46(10):2950-2956.
Abstract:
Nano-B4CP particulates (n-B4CP) reinforced 2009Al matrix composites with different reinforcement volume fractions (0, 2, 4 and 6vol.%) were fabricated by powder metallurgy combined with hot extrusion. The effects of different volume fractions of n-B4CP on microstructure, solution and aging behavior and mechanical properties of n-B4CP/2009Al composites were studied by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), vickers hardness measuring instrument and so on. The results show that, the n-B4CP were uniformly dispersed in the composites after hot extrusion process. The best solution temperature and time of the composites were 495℃ and 1 h, the resolution of second phase particles (Al2Cu) were dissolved back into the matrix and only a small amount remaining in the matrix during solution treatment process. N-B4CP/2009Al composites with different volume fractions (0, 2, 4 and 6vol.%) treated at 495℃ for 1h and then ageing at 175℃for 14h almost simultaneously reached the peak hardness, and the aging peak time decreased 2h compared to matrix alloy. After peak aging, the microstructure of composites were observed by TEM, indicating that the growth of precipitation was strongly restrained due to the addition of n-B4CP particulates. Compared to the matrix alloy, the composites with higher density of ?ner precipitates led to an earlier attainment in the peak aging condition. After the optimum heat treatment process, the tensile strength of the composites increases at first and then decreases along with the increasing of n-B4CP volume fraction, while the yield strength always increases. High volume fraction of n-B4CP effectively play the role of pinning dislocations, but the phenomenon of agglomeration of high volume fraction of n-B4CP results in composites’ early cracking.
Nano-B4CP particulates (n-B4CP) reinforced 2009Al matrix composites with different reinforcement volume fractions (0, 2, 4 and 6vol.%) were fabricated by powder metallurgy combined with hot extrusion. The effects of different volume fractions of n-B4CP on microstructure, solution and aging behavior and mechanical properties of n-B4CP/2009Al composites were studied by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), vickers hardness measuring instrument and so on. The results show that, the n-B4CP were uniformly dispersed in the composites after hot extrusion process. The best solution temperature and time of the composites were 495℃ and 1 h, the resolution of second phase particles (Al2Cu) were dissolved back into the matrix and only a small amount remaining in the matrix during solution treatment process. N-B4CP/2009Al composites with different volume fractions (0, 2, 4 and 6vol.%) treated at 495℃ for 1h and then ageing at 175℃for 14h almost simultaneously reached the peak hardness, and the aging peak time decreased 2h compared to matrix alloy. After peak aging, the microstructure of composites were observed by TEM, indicating that the growth of precipitation was strongly restrained due to the addition of n-B4CP particulates. Compared to the matrix alloy, the composites with higher density of ?ner precipitates led to an earlier attainment in the peak aging condition. After the optimum heat treatment process, the tensile strength of the composites increases at first and then decreases along with the increasing of n-B4CP volume fraction, while the yield strength always increases. High volume fraction of n-B4CP effectively play the role of pinning dislocations, but the phenomenon of agglomeration of high volume fraction of n-B4CP results in composites’ early cracking.
2017, 46(10):2957-2962.
Abstract:
Variable curvature 2-section of 2099 Al-Li alloy is important truss of Chinese independently developed large airplane C919, four roll bending forming is main method to manufacture this kind of part. Due to the high specific strength of Al-Li alloy and asymmetric structure of 2-section, compared to section of conventional aluminum alloy, 2-section of Al-Li alloy was extremely prone to oblique bending. Therefore, four roll bending process of 2-section was simulated by finite element software ABAQUS, effect of roller gap, clearance between bottom roller and profile in vertical direction, displacement in X direction of left and right rollers was researched on oblique bending during four roll bending of 2-section, best roll bending process parameters was confirmed. Roll bending process experiment was carried based on it. The results show that 0.2 mm for roller gap, 0.3 mm for clearance between bottom roller and profile in vertical direction, 1.5 mm for displacement in X direction of left and right rollers can effectively solve the problem of oblique bending for roll bending of 2-section.
Variable curvature 2-section of 2099 Al-Li alloy is important truss of Chinese independently developed large airplane C919, four roll bending forming is main method to manufacture this kind of part. Due to the high specific strength of Al-Li alloy and asymmetric structure of 2-section, compared to section of conventional aluminum alloy, 2-section of Al-Li alloy was extremely prone to oblique bending. Therefore, four roll bending process of 2-section was simulated by finite element software ABAQUS, effect of roller gap, clearance between bottom roller and profile in vertical direction, displacement in X direction of left and right rollers was researched on oblique bending during four roll bending of 2-section, best roll bending process parameters was confirmed. Roll bending process experiment was carried based on it. The results show that 0.2 mm for roller gap, 0.3 mm for clearance between bottom roller and profile in vertical direction, 1.5 mm for displacement in X direction of left and right rollers can effectively solve the problem of oblique bending for roll bending of 2-section.
2017, 46(10):2963-2968.
Abstract:
In this paper, an anionic surfactant, i.e. sodium dodecyl sulfate (SDS) was employed for preparation of the IrO2-Ta2O5/SnO2-Sb-MnO2/Ti electrodes through the pyrolysis process. The microstructure and phase composition of the electrodes were analyzed via scanning electron microscopy (SEM) and X-ray diffraction (XRD), and the cyclic voltammetry (CV) and polarization curves were also measured to evaluate their electro-catalytic activity by using an electrochemical station (type CS310). The obtained results revealed that the employment of the SDS could effectively improve the microstructure as well as enhance the electro-catalytic ability of the electrodes. Under the conditions of this study, the optimum dosage of SDS was 1.6 g/L for preparation of the IrO2-Ta2O5/SnO2-Sb-MnO2/Ti electrodes and the crystallization degree as high as 99.83% could be obtained. The electrode performances and stability were further investigated by anodic oxidation of phenol and accelerated life test. The experimental data depicted the phenol and chemical oxygen demand (COD) removal efficiency were increased from 68.5% and 60.1% to 79.2% and 67.5% when electrodes without and with dosage of 1.6 g/L were used, respectively, for phenol degradation at conditions of current density of 15 mA/cm2 and reaction time of 180 min; moreover, the accelerated life were raised to 68 h, which is much longer than that of the former (52 h).
In this paper, an anionic surfactant, i.e. sodium dodecyl sulfate (SDS) was employed for preparation of the IrO2-Ta2O5/SnO2-Sb-MnO2/Ti electrodes through the pyrolysis process. The microstructure and phase composition of the electrodes were analyzed via scanning electron microscopy (SEM) and X-ray diffraction (XRD), and the cyclic voltammetry (CV) and polarization curves were also measured to evaluate their electro-catalytic activity by using an electrochemical station (type CS310). The obtained results revealed that the employment of the SDS could effectively improve the microstructure as well as enhance the electro-catalytic ability of the electrodes. Under the conditions of this study, the optimum dosage of SDS was 1.6 g/L for preparation of the IrO2-Ta2O5/SnO2-Sb-MnO2/Ti electrodes and the crystallization degree as high as 99.83% could be obtained. The electrode performances and stability were further investigated by anodic oxidation of phenol and accelerated life test. The experimental data depicted the phenol and chemical oxygen demand (COD) removal efficiency were increased from 68.5% and 60.1% to 79.2% and 67.5% when electrodes without and with dosage of 1.6 g/L were used, respectively, for phenol degradation at conditions of current density of 15 mA/cm2 and reaction time of 180 min; moreover, the accelerated life were raised to 68 h, which is much longer than that of the former (52 h).
2017, 46(10):2969-2974.
Abstract:
The electrochemical behaviors of Alloy 690 was studied in simulated PWR secondary loop high temperature and high pressure alkaline water environments controlling pH (pH@25℃=9.5) with ammonia-water by measuring open circuit potentials (OCP), electrochemical impedance spectroscopies (EIS), potentiodynamic (PD) polarization curves and thermomechanical analysis. The results showed that: After immersing in ammonia-water at the given temperature (50, 100, 150, 200, 250 or 285℃) for 20h, the OCPs of Alloy 690 have reached a rather steady state and the double-layer oxide films have formed on the Alloy 690. With the increasing temperature, the resistances of outer oxide layer firstly decrease and then increase, while the resistances of the inner oxide layer and the protection of the whole oxide films decrease. In addition, the solution pH@T decreases with the increasing temperature. All of the above causes the decline of OCPs, corrosion current densities and passive current densities from the PD curves.
The electrochemical behaviors of Alloy 690 was studied in simulated PWR secondary loop high temperature and high pressure alkaline water environments controlling pH (pH@25℃=9.5) with ammonia-water by measuring open circuit potentials (OCP), electrochemical impedance spectroscopies (EIS), potentiodynamic (PD) polarization curves and thermomechanical analysis. The results showed that: After immersing in ammonia-water at the given temperature (50, 100, 150, 200, 250 or 285℃) for 20h, the OCPs of Alloy 690 have reached a rather steady state and the double-layer oxide films have formed on the Alloy 690. With the increasing temperature, the resistances of outer oxide layer firstly decrease and then increase, while the resistances of the inner oxide layer and the protection of the whole oxide films decrease. In addition, the solution pH@T decreases with the increasing temperature. All of the above causes the decline of OCPs, corrosion current densities and passive current densities from the PD curves.
2017, 46(10):2975-2980.
Abstract:
Influence of deformation refinement grain and lubrication rolling on the cube texture formation in Ni-9.3at.%W(Ni9.3W) alloy substrate was analysised by optical microscope(OM), X-ray diffraction(XRD) and electron backscattered diffraction(EBSD) technique. The results show that the method of deformation refinement grain can effectively improve the cube texture content in Ni9.3W alloy substrate. The grains are finer according to the increase of deformation reduction, which results in obtaining a higher cube texture content in annealed substrate.The cube texture content by the optimized deformation refinement grain increases 9.8% higher than that without deformation refinement grain in Ni9.3W alloy substrate. Besides, cube texture content increases further 24.7% by adding total rolling deformation after deformation refinement grain. According to these results, the parameters for preparation of the initial ingot are determined. On the basis of it, the influence of lubrication rolling on cube texture formation is also studied by compared with that without lubrication rolling. Lubrication rolling is able to get more S and Copper orientation in rolling textures. After recrystallization annealing, cube texture content with lubrication rolling reaches 86.7% (<15°), which is 9.6% higher than that without lubrication rolling. In addition, the twin boundary quantity and low angle grain boundary content by lubrication rolling is superior to that without lubrication rolling, which illustrates that lubrication rolling has a significant effect on the cube texture formation.
Influence of deformation refinement grain and lubrication rolling on the cube texture formation in Ni-9.3at.%W(Ni9.3W) alloy substrate was analysised by optical microscope(OM), X-ray diffraction(XRD) and electron backscattered diffraction(EBSD) technique. The results show that the method of deformation refinement grain can effectively improve the cube texture content in Ni9.3W alloy substrate. The grains are finer according to the increase of deformation reduction, which results in obtaining a higher cube texture content in annealed substrate.The cube texture content by the optimized deformation refinement grain increases 9.8% higher than that without deformation refinement grain in Ni9.3W alloy substrate. Besides, cube texture content increases further 24.7% by adding total rolling deformation after deformation refinement grain. According to these results, the parameters for preparation of the initial ingot are determined. On the basis of it, the influence of lubrication rolling on cube texture formation is also studied by compared with that without lubrication rolling. Lubrication rolling is able to get more S and Copper orientation in rolling textures. After recrystallization annealing, cube texture content with lubrication rolling reaches 86.7% (<15°), which is 9.6% higher than that without lubrication rolling. In addition, the twin boundary quantity and low angle grain boundary content by lubrication rolling is superior to that without lubrication rolling, which illustrates that lubrication rolling has a significant effect on the cube texture formation.
2017, 46(10):2981-2986.
Abstract:
The effects of cold deformation treatment on solution microstructures and properties of a new designed Al-13.01Zn-3.16Mg-2.8Cu-0.204Zr-0.0757Sr alloy extrusions were investigated by tensile, hardness tests, XRD and EBSD analysis, inter-granular and exfoliation corrosion resistance experiments. The results show that compared to the traditional solution - aging, The average grain size decreases, the hardness, conductivity, low-angle grain boundaries ratio, tensile and yield strength increases, and corrosion resistance becomes better of the alloy under solution-compression-aging. Wherein the hardness, conductivity, yield, tensile strength reached 243.0 HV, 25.085% IACS, 734.7 MPa and 683.2 MPa, elongation of 6.1% and intergranular corrosion depth of 23.81 um, intergranular corrosion rate 2 of the alloy under the solution- compression - aging (100 ℃×24 h).
The effects of cold deformation treatment on solution microstructures and properties of a new designed Al-13.01Zn-3.16Mg-2.8Cu-0.204Zr-0.0757Sr alloy extrusions were investigated by tensile, hardness tests, XRD and EBSD analysis, inter-granular and exfoliation corrosion resistance experiments. The results show that compared to the traditional solution - aging, The average grain size decreases, the hardness, conductivity, low-angle grain boundaries ratio, tensile and yield strength increases, and corrosion resistance becomes better of the alloy under solution-compression-aging. Wherein the hardness, conductivity, yield, tensile strength reached 243.0 HV, 25.085% IACS, 734.7 MPa and 683.2 MPa, elongation of 6.1% and intergranular corrosion depth of 23.81 um, intergranular corrosion rate 2 of the alloy under the solution- compression - aging (100 ℃×24 h).
2017, 46(10):2993-2998.
Abstract:
Six kinds of Ti-6Al-4V artificial bone scaffold were designed and built with SLM (Selective Laser Melting) technology. Universal material testing machine and high-speed camera were used to analyze the compression process of scaffolds, and ANSYS was used to analyze the stress of scaffold. The results showed that the vertical column diameter had a great influence on the mechanical property parameters of scaffolds but the beam diameter had little influence on them, under the same height, the increasing of beam diameter and layer or support column diameter, which result in structure length-diameter ratio decrease, so that structure firm and load-carrying capacity were improved and the mechanical property should match the surrounding bone tissue. Through the analysis, mechanical property parameters of three kinds of scaffolds were close to human femur, so they can be used as the artificial bone scaffolds of femur.
Six kinds of Ti-6Al-4V artificial bone scaffold were designed and built with SLM (Selective Laser Melting) technology. Universal material testing machine and high-speed camera were used to analyze the compression process of scaffolds, and ANSYS was used to analyze the stress of scaffold. The results showed that the vertical column diameter had a great influence on the mechanical property parameters of scaffolds but the beam diameter had little influence on them, under the same height, the increasing of beam diameter and layer or support column diameter, which result in structure length-diameter ratio decrease, so that structure firm and load-carrying capacity were improved and the mechanical property should match the surrounding bone tissue. Through the analysis, mechanical property parameters of three kinds of scaffolds were close to human femur, so they can be used as the artificial bone scaffolds of femur.
2017, 46(10):2999-3004.
Abstract:
In this paper a Ni-based superalloyalloy was fabricated by laser additive manufacturing technology(LEN98M) and by trainditional directional solidification (DZ98M), respectively. The solidification morphology, microstructures, elements segregation are systematically investigated by using optical microscope(OM), scanning electron microscope(SEM), energy dispersive spectroscopy(EDS), X-ray diffraction(XRD), electron microprobe(EPMA), differential thermal analysis(DTA). The results show that the primary dendrite arm spacing of the LEN98M alloy is 70 μm and reduced as 1/5 of the DZ98M alloy. There is a serious segregation of alloying elements in the range of dendrite scale. The morphology of γ? phase are irregular and no precipitation of carbides observed in as-casted LEN98M alloy. There are smaller γ/γ? eutectic dispersed in interdendritic regions.
In this paper a Ni-based superalloyalloy was fabricated by laser additive manufacturing technology(LEN98M) and by trainditional directional solidification (DZ98M), respectively. The solidification morphology, microstructures, elements segregation are systematically investigated by using optical microscope(OM), scanning electron microscope(SEM), energy dispersive spectroscopy(EDS), X-ray diffraction(XRD), electron microprobe(EPMA), differential thermal analysis(DTA). The results show that the primary dendrite arm spacing of the LEN98M alloy is 70 μm and reduced as 1/5 of the DZ98M alloy. There is a serious segregation of alloying elements in the range of dendrite scale. The morphology of γ? phase are irregular and no precipitation of carbides observed in as-casted LEN98M alloy. There are smaller γ/γ? eutectic dispersed in interdendritic regions.
2017, 46(10):3005-3010.
Abstract:
The variation of microstructure evolution, phase composition, solidification path and tensile properties of high Nb-TiAl alloys alloyed with β stable elements Cr or/and Mn were studied in this work. The results showed that volume fraction of B2 phase gradually increased while α2 phase gradually decreased in as-cast microstructures of Ti-45Al-8Nb-0.4B (atom fraction, %, similarly hereinafter) alloyed by 2Cr, 2Mn and 1Cr1Mn. 1Cr1Mn alloy turned into the novel β-γ high Nb-TiAl alloy, which was composed of γ and B2 two phases rather than γ, α2 and B2 three phases. The solidification path changed from L→β→β+α→α+γ+β→α2+γ+B2 to L→β→β+γ→B2+γ. The co-addition of Cr and Mn had more obvious β stable ability. The room temperature tensile results showed that with the increase of B2 phase, the strength and elongation both decreased. While the elongation decreased firstly and increased subsequently at 900℃. This phenomenon showed that when the β phase content reach a certain level, which was 14.4 % in this study, β phase was advantageous to deformation at high temperature.
The variation of microstructure evolution, phase composition, solidification path and tensile properties of high Nb-TiAl alloys alloyed with β stable elements Cr or/and Mn were studied in this work. The results showed that volume fraction of B2 phase gradually increased while α2 phase gradually decreased in as-cast microstructures of Ti-45Al-8Nb-0.4B (atom fraction, %, similarly hereinafter) alloyed by 2Cr, 2Mn and 1Cr1Mn. 1Cr1Mn alloy turned into the novel β-γ high Nb-TiAl alloy, which was composed of γ and B2 two phases rather than γ, α2 and B2 three phases. The solidification path changed from L→β→β+α→α+γ+β→α2+γ+B2 to L→β→β+γ→B2+γ. The co-addition of Cr and Mn had more obvious β stable ability. The room temperature tensile results showed that with the increase of B2 phase, the strength and elongation both decreased. While the elongation decreased firstly and increased subsequently at 900℃. This phenomenon showed that when the β phase content reach a certain level, which was 14.4 % in this study, β phase was advantageous to deformation at high temperature.
2017, 46(10):3011-3016.
Abstract:
Creep limit loads for TA2 made pressure vessels have been carried out by finite element (FE) method based on the isochronous stress-strain curves of commercial pure titanium at ambient temperature. Take the cylindrical pressure vessels as example, results mainly shows that creep limit loads will firstly decrease quickly and then decrease slowly with the time increasing. The influence effect of the ratio K on creep limit load has been conducted in detail, which provides estimating solutions for ambient temperature creep limit load prediction. These solutions can reflect the effect of the time degradation of limit load, and also the allowable strain and K on the limit load. This research will provide some valuable references to the safety assessment of titanium made pressure equipment.
Creep limit loads for TA2 made pressure vessels have been carried out by finite element (FE) method based on the isochronous stress-strain curves of commercial pure titanium at ambient temperature. Take the cylindrical pressure vessels as example, results mainly shows that creep limit loads will firstly decrease quickly and then decrease slowly with the time increasing. The influence effect of the ratio K on creep limit load has been conducted in detail, which provides estimating solutions for ambient temperature creep limit load prediction. These solutions can reflect the effect of the time degradation of limit load, and also the allowable strain and K on the limit load. This research will provide some valuable references to the safety assessment of titanium made pressure equipment.
2017, 46(10):3017-3022.
Abstract:
6063Al- (K2ZrF6+KBF4) was used as the reaction system, in situ ZrB2/6063 aluminum matrix composites were prepared by extrusion. The microstructure changes of the composites before and after extrusion were studied, and the influence of extrusion process on the friction and wear properties of the composites was studied. The results showed that the composite materials were prepared by casting in situ. The grain size of the matrix was 30~50μm, and the ZrB2 particles were regular polygons. After extrusion processing, the grain size of the composite was fine, and the size was 7~14μm, and the particle size was uniform, and the size was 1~3μm, and agglomeration was improved. Because the particle size distribution was more uniform after extrusion, the particle was more round and blunt, which made the surface of the wear scar more smooth, and the difference of the concave and convex of each part was reduced, in the process of loading, the friction coefficient of the main changed in the range of 0.29~0.40, when the load was 12N, the minimum friction coefficient was 0.29 and the minimum friction coefficient compared to the original ingot of composite materials was reduced by 32.4%. So the friction reduction of the composites was greatly improved after extrusion., and the wear volume and wear scar width were decreased due to the increase of the friction reduction,and the wear resistance had also been greatly improved.Through SEM analysis, it can be known that the wear mechanism of the composites was mainly abrasive wear and slight adhesive wear.
6063Al- (K2ZrF6+KBF4) was used as the reaction system, in situ ZrB2/6063 aluminum matrix composites were prepared by extrusion. The microstructure changes of the composites before and after extrusion were studied, and the influence of extrusion process on the friction and wear properties of the composites was studied. The results showed that the composite materials were prepared by casting in situ. The grain size of the matrix was 30~50μm, and the ZrB2 particles were regular polygons. After extrusion processing, the grain size of the composite was fine, and the size was 7~14μm, and the particle size was uniform, and the size was 1~3μm, and agglomeration was improved. Because the particle size distribution was more uniform after extrusion, the particle was more round and blunt, which made the surface of the wear scar more smooth, and the difference of the concave and convex of each part was reduced, in the process of loading, the friction coefficient of the main changed in the range of 0.29~0.40, when the load was 12N, the minimum friction coefficient was 0.29 and the minimum friction coefficient compared to the original ingot of composite materials was reduced by 32.4%. So the friction reduction of the composites was greatly improved after extrusion., and the wear volume and wear scar width were decreased due to the increase of the friction reduction,and the wear resistance had also been greatly improved.Through SEM analysis, it can be known that the wear mechanism of the composites was mainly abrasive wear and slight adhesive wear.
2017, 46(10):3023-3027.
Abstract:
Ag-Sn(9.7-χ/10)-In(χ=0,0.5,1.0,1.5,2.0) alloy powders were prepared by atomization. Within the Ag-Sn-In alloy powders were oxidized in air. The experimental indicates show that the oxidation rate of the samples of χ = 0.5 was always lower than that of the samples of χ = 0, a little added In cannot promote the increase of oxidation rate, instead inhibits its oxidation. The oxidation rate of the samples of χ = (1.0,1.5,2.0) varies oddly. When the temperature is below 700℃, their oxidation rate is higher than the samples of χ = 0 obviously, while the oxidizing temperature and holding time reaches a certain parameters, the oxidation rate of samples of χ = 0 is better. It shows that when it is at low oxidizing temperature for short time, added In of χ = (1.0,1.5,2.0) is good for oxidation reaction, but at high temperature oxidation for a long time, the effect of the additive In is not big, even negative on the oxidation reaction. According to the comprehensive test, we explore and conclude that the reasonable oxidizing temperature which the various samples can obtain a better oxidation rate is at 750 ℃.
Ag-Sn(9.7-χ/10)-In(χ=0,0.5,1.0,1.5,2.0) alloy powders were prepared by atomization. Within the Ag-Sn-In alloy powders were oxidized in air. The experimental indicates show that the oxidation rate of the samples of χ = 0.5 was always lower than that of the samples of χ = 0, a little added In cannot promote the increase of oxidation rate, instead inhibits its oxidation. The oxidation rate of the samples of χ = (1.0,1.5,2.0) varies oddly. When the temperature is below 700℃, their oxidation rate is higher than the samples of χ = 0 obviously, while the oxidizing temperature and holding time reaches a certain parameters, the oxidation rate of samples of χ = 0 is better. It shows that when it is at low oxidizing temperature for short time, added In of χ = (1.0,1.5,2.0) is good for oxidation reaction, but at high temperature oxidation for a long time, the effect of the additive In is not big, even negative on the oxidation reaction. According to the comprehensive test, we explore and conclude that the reasonable oxidizing temperature which the various samples can obtain a better oxidation rate is at 750 ℃.
2017, 46(10):3028-3032.
Abstract:
Directionally solidified Manesium alloys AZ91 with element Y were produced by using the liquid metal cooling Bridgman furnance. The dendrite morphology and microstructure of AZ91 were investigated in present paper. The results indicated that the primary dendrites of AZ91 grow along the direction of heat flow. The are six secondary dendrites which around the primary dendrite likes petal shape can be observed in cross section. The microstructure of AZ91 alloy is mainly composed of a matrix of primary a(Mg) solid solution and eutectic b(Mg17Al12) phase, and some Y-rich phase can be found with Y additions by using SEM and EDS. The RE-rich phases present coarse rod-like shape or tiny graininess. The Y, Mg, Al and Mn elements are found in RE-rich phase, and the mass fraction of rare earth element Y is about 22%.
Directionally solidified Manesium alloys AZ91 with element Y were produced by using the liquid metal cooling Bridgman furnance. The dendrite morphology and microstructure of AZ91 were investigated in present paper. The results indicated that the primary dendrites of AZ91 grow along the direction of heat flow. The are six secondary dendrites which around the primary dendrite likes petal shape can be observed in cross section. The microstructure of AZ91 alloy is mainly composed of a matrix of primary a(Mg) solid solution and eutectic b(Mg17Al12) phase, and some Y-rich phase can be found with Y additions by using SEM and EDS. The RE-rich phases present coarse rod-like shape or tiny graininess. The Y, Mg, Al and Mn elements are found in RE-rich phase, and the mass fraction of rare earth element Y is about 22%.
2017, 46(10):3033-3037.
Abstract:
The subjects of this paper is ultra-high strength aluminum alloy Al-10.78Zn-2.78Mg-2.59Cu-0.22Zr-0.047Sr, which was involved in the process of solution - aging and thermomechanical treatment(solution-overaging-hot compression) - solution - aging. Electron back scattering diffractions (EBSD) technology, X-ray diffraction (XRD) and tensile testing were respectively used on its study of distribution of grain and grain boundaries, internal dislocation density and tensile properties, and dislocation strengthening and grain boundary strengthening are calculated quantitatively. The results show that TMT refines grain with average grain size reducing from 7.30 μm to 6.04 μm and misorientation angle reducing from 21.45 to 21.04 . TMT increases peak aging hardness from 214.6 HV(120℃×48h) to 226.8 HV(100℃×48h), but has little effect on strength with yield strength are both almost 600 MPa. The tensile fracture morphology of alloys both?display intergranular and tear fracture. Dislocation density of alloys processed by solution and TMT - solution are both 0, and TMT reduces sum of dislocation strengthening and grain boundary strengthening from 58.8 MPa to 57.4 MPa.
The subjects of this paper is ultra-high strength aluminum alloy Al-10.78Zn-2.78Mg-2.59Cu-0.22Zr-0.047Sr, which was involved in the process of solution - aging and thermomechanical treatment(solution-overaging-hot compression) - solution - aging. Electron back scattering diffractions (EBSD) technology, X-ray diffraction (XRD) and tensile testing were respectively used on its study of distribution of grain and grain boundaries, internal dislocation density and tensile properties, and dislocation strengthening and grain boundary strengthening are calculated quantitatively. The results show that TMT refines grain with average grain size reducing from 7.30 μm to 6.04 μm and misorientation angle reducing from 21.45 to 21.04 . TMT increases peak aging hardness from 214.6 HV(120℃×48h) to 226.8 HV(100℃×48h), but has little effect on strength with yield strength are both almost 600 MPa. The tensile fracture morphology of alloys both?display intergranular and tear fracture. Dislocation density of alloys processed by solution and TMT - solution are both 0, and TMT reduces sum of dislocation strengthening and grain boundary strengthening from 58.8 MPa to 57.4 MPa.
2017, 46(10):3038-3042.
Abstract:
The characteristics of microstructures, thermal properties, wettabilities and mechanical properties of Sn-Bi-In solders with different content were studied. The results show that the microstructure of Sn-Bi-In solders consists of β-Sn, Bi and InBi phases, the reduction of Bi content can result in the proportion decrease of Bi and InBi phases. There are three endothermic peaks with different magnitudes on the DSC curves, and the onset melting temperature of solders are around 101.3-103.4℃, with the increase of Sn concentration, the melting range of solders firstly decreases and then increases, while the spreading area firstly increases and then decreases. The mircrohardness of solders increases with the rising of Bi conetent, in addition, the hardness is remarkably higher than Sn-Bi eutectic alloy when the In element is added to solder. The tensile strength and elongation of solders decrease with reduction of Bi content.
The characteristics of microstructures, thermal properties, wettabilities and mechanical properties of Sn-Bi-In solders with different content were studied. The results show that the microstructure of Sn-Bi-In solders consists of β-Sn, Bi and InBi phases, the reduction of Bi content can result in the proportion decrease of Bi and InBi phases. There are three endothermic peaks with different magnitudes on the DSC curves, and the onset melting temperature of solders are around 101.3-103.4℃, with the increase of Sn concentration, the melting range of solders firstly decreases and then increases, while the spreading area firstly increases and then decreases. The mircrohardness of solders increases with the rising of Bi conetent, in addition, the hardness is remarkably higher than Sn-Bi eutectic alloy when the In element is added to solder. The tensile strength and elongation of solders decrease with reduction of Bi content.
46 Effect Study of Composition and Sintering Temperature on Reaction Heat of Fe-Al Reactive Material
2017, 46(10):3043-3047.
Abstract:
Micron Al, Fe powders were used as raw materials to prepare compacts, in which the quality ratio of Fe: Al were 3:7, 4:6 and 5:5 respectively by cold isostatic pressing. The effects of Fe-Al different composition proportion on reaction heat of compacts were studied by differential scanning calorimetry, in order to confirm the compact composition with maximum reaction heat. The Fe-Al reactive material with the above composition was prepared by pressureless sintering, and the influence of sintering temperature on the microstructure and reaction heat were investigated. Results show that, compact with the quality ratio of Fe: Al = 4:6 can release the maximum reaction heat: -589.8 J/g. When the sintering temperature was 540 ℃, a small amount of intermetallic compounds: Al13Fe4 and Fe2Al5 generated, which reduces the reaction heat, and is not conducive to the further spread of the reaction. However, when the sintering temperature was 530 ℃, no obvious intermetallic compound generated, resulting in the reaction heat decreasing slightly to -538.5 J/g.
Micron Al, Fe powders were used as raw materials to prepare compacts, in which the quality ratio of Fe: Al were 3:7, 4:6 and 5:5 respectively by cold isostatic pressing. The effects of Fe-Al different composition proportion on reaction heat of compacts were studied by differential scanning calorimetry, in order to confirm the compact composition with maximum reaction heat. The Fe-Al reactive material with the above composition was prepared by pressureless sintering, and the influence of sintering temperature on the microstructure and reaction heat were investigated. Results show that, compact with the quality ratio of Fe: Al = 4:6 can release the maximum reaction heat: -589.8 J/g. When the sintering temperature was 540 ℃, a small amount of intermetallic compounds: Al13Fe4 and Fe2Al5 generated, which reduces the reaction heat, and is not conducive to the further spread of the reaction. However, when the sintering temperature was 530 ℃, no obvious intermetallic compound generated, resulting in the reaction heat decreasing slightly to -538.5 J/g.
2017, 46(10):3048-3052.
Abstract:
W17.9Ni65.6B13.5V3(at. %)amorphous alloy was prepared by melt spinning method. X-ray diffraction pattern and differential scanning calorimeter were applied to investigate non-isothermal crystallization kinetics of the amorphous alloy. As the heating rate was increased, the values of the glass transition temperature, the initial crystallization temperature and the peak temperature were gone up, suggesting that the amorphous alloy had obvious crystallization kinetics. The crystallization activation energy of W17.9Ni65.6B13.5V3 amorphous alloy calculated by Kissinger equations and Ozawa equations was 456.9kJ/mol and 471.1kJ/mol, respectively, indicating that the amorphous alloy possessed high thermal stability. The values of crystallization activation energy Ex were smaller than nucleation activation energy Ep calculated by Kissinger equation and Ozawa equation at the characteristics of the temperature, which showed that nucleation process more easily than the grain growth process, indicating that ultrafine grains structure could be easily obtained at certain conditions.
W17.9Ni65.6B13.5V3(at. %)amorphous alloy was prepared by melt spinning method. X-ray diffraction pattern and differential scanning calorimeter were applied to investigate non-isothermal crystallization kinetics of the amorphous alloy. As the heating rate was increased, the values of the glass transition temperature, the initial crystallization temperature and the peak temperature were gone up, suggesting that the amorphous alloy had obvious crystallization kinetics. The crystallization activation energy of W17.9Ni65.6B13.5V3 amorphous alloy calculated by Kissinger equations and Ozawa equations was 456.9kJ/mol and 471.1kJ/mol, respectively, indicating that the amorphous alloy possessed high thermal stability. The values of crystallization activation energy Ex were smaller than nucleation activation energy Ep calculated by Kissinger equation and Ozawa equation at the characteristics of the temperature, which showed that nucleation process more easily than the grain growth process, indicating that ultrafine grains structure could be easily obtained at certain conditions.
2017, 46(10):3053-3057.
Abstract:
Abstract：The self-healing effect on corrosion behaviors of Pd79Cu4Au2Si10P5 amorphous alloy in 3 wt.% NaCl and 1 mol/L HCl solutions was studied by potentiodynamic polarization experiments and electrochemical impedance spectroscopy (EIS). The results of potentiodynamic polarization experiments show that the self-healing sample has better corrosion resistance than the unrepaired sample, but the as-cast sample has the best corrosion resistance. EIS results show that the Nyquist figures of all the studied samples are composed of one single semi-circle in the state of open circuit potential. The repaired sample has a higher charge transfer reaction resistance than the unrepaired sample, and the as-cast sample has the highest charge transfer reaction resistance. This result is accord with that of potentiodynamic polarization. Surface analysis by SEM shows that all the samples are eroded by pitting corrosion. The pitting density on the surface of the as-cast sample is the least, and that of the un-healing sample is the most.
Abstract：The self-healing effect on corrosion behaviors of Pd79Cu4Au2Si10P5 amorphous alloy in 3 wt.% NaCl and 1 mol/L HCl solutions was studied by potentiodynamic polarization experiments and electrochemical impedance spectroscopy (EIS). The results of potentiodynamic polarization experiments show that the self-healing sample has better corrosion resistance than the unrepaired sample, but the as-cast sample has the best corrosion resistance. EIS results show that the Nyquist figures of all the studied samples are composed of one single semi-circle in the state of open circuit potential. The repaired sample has a higher charge transfer reaction resistance than the unrepaired sample, and the as-cast sample has the highest charge transfer reaction resistance. This result is accord with that of potentiodynamic polarization. Surface analysis by SEM shows that all the samples are eroded by pitting corrosion. The pitting density on the surface of the as-cast sample is the least, and that of the un-healing sample is the most.
2017, 46(10):3058-3062.
Abstract:
In light of the common problem of hydrogen evolution in traditional electroforming nickel and the huge advantages of this new medium ionic liquid, the effects of temperature, current density on electroformed nickel’s morphology and structure as well as the tensile strength and microhardness of electroformed nickel from ionic liquid were first studied in this paper. The results show that the suitable temperature range are from 110 ℃ to 130 ℃. XRD tests show electroforming temperature can also significantly improve the degree of crystallinity of electroformed nickel layer, and promote the transformation of preferred orientation of grains from (111) to (200). 1 mA/cm2 is the best current density. With the increasing of it, the surface of Ni looks rougher and rougher, but grain size and the degree of crystallinity of Ni decreases. In addition, compared with aqueous solution, Ni electroformed from ionic liquid has higher tensile strength and microhardness.
In light of the common problem of hydrogen evolution in traditional electroforming nickel and the huge advantages of this new medium ionic liquid, the effects of temperature, current density on electroformed nickel’s morphology and structure as well as the tensile strength and microhardness of electroformed nickel from ionic liquid were first studied in this paper. The results show that the suitable temperature range are from 110 ℃ to 130 ℃. XRD tests show electroforming temperature can also significantly improve the degree of crystallinity of electroformed nickel layer, and promote the transformation of preferred orientation of grains from (111) to (200). 1 mA/cm2 is the best current density. With the increasing of it, the surface of Ni looks rougher and rougher, but grain size and the degree of crystallinity of Ni decreases. In addition, compared with aqueous solution, Ni electroformed from ionic liquid has higher tensile strength and microhardness.
2017, 46(10):3063-3067.
Abstract:
Ti-1023 titanium alloy has attracted considerable attentions as aircraft structural material because of its high speci?c strength, good fracture toughness, and excellent stress corrosion resistance and enhanced processing characteristics. However, the shortcoming in Fe element segregation in large specification ingot retarded its practical application. Magnetic filed can be used in overcoming this deficiency at certain degree. In this paper, The influence of magnetic filed on the solidification macrostructure and Fe content of Ti-1023 under vacuum arc remelting was investigated．The results show that when the Magnetic filed T (T=10Gs, T=30Gs) the solidified microstructure is composed of bulky columnar crystal, small bamboo-like columnar crystal and equiaxed grains. When the Magnetic filed T=20Gsthe solidified microstructure is completely composed of bulky columnar crystal and equiaxed grains. The law of Fe segregation abide by normal segregation ,Fe content increases gradually from the bottom to the top of ingots along axial direction and the degree of macro segregation is greater in the radial direction in the middle of the ingot versus the top and bottom., The macrosegregation rate of Fe element increases ?rstly and then decreases with different Magnetic filed.
Ti-1023 titanium alloy has attracted considerable attentions as aircraft structural material because of its high speci?c strength, good fracture toughness, and excellent stress corrosion resistance and enhanced processing characteristics. However, the shortcoming in Fe element segregation in large specification ingot retarded its practical application. Magnetic filed can be used in overcoming this deficiency at certain degree. In this paper, The influence of magnetic filed on the solidification macrostructure and Fe content of Ti-1023 under vacuum arc remelting was investigated．The results show that when the Magnetic filed T (T=10Gs, T=30Gs) the solidified microstructure is composed of bulky columnar crystal, small bamboo-like columnar crystal and equiaxed grains. When the Magnetic filed T=20Gsthe solidified microstructure is completely composed of bulky columnar crystal and equiaxed grains. The law of Fe segregation abide by normal segregation ,Fe content increases gradually from the bottom to the top of ingots along axial direction and the degree of macro segregation is greater in the radial direction in the middle of the ingot versus the top and bottom., The macrosegregation rate of Fe element increases ?rstly and then decreases with different Magnetic filed.
2017, 46(10):3068-3072.
Abstract:
A modified surface layer was fabricated on Ti-6Al-4V alloy by means of wet peening treatment. The fatigue life of specimen which suffered wet peening treatment was obviously increased. Compared with the fracture of un-peened sample, the fatigue crack initial site was transferred from surface to the interior region beneath the surface (about 1 mm depth). The co-action of grain refinement strengthening and dislocation strengthening dominated the transferred fatigue crack initial site. The compressive residual stress effectively delayed the crack propagation. The grain refinement strengthening, the dislocation strengthening as well as the compressive residual stress were the main factors of increased fatigue life.
A modified surface layer was fabricated on Ti-6Al-4V alloy by means of wet peening treatment. The fatigue life of specimen which suffered wet peening treatment was obviously increased. Compared with the fracture of un-peened sample, the fatigue crack initial site was transferred from surface to the interior region beneath the surface (about 1 mm depth). The co-action of grain refinement strengthening and dislocation strengthening dominated the transferred fatigue crack initial site. The compressive residual stress effectively delayed the crack propagation. The grain refinement strengthening, the dislocation strengthening as well as the compressive residual stress were the main factors of increased fatigue life.
2017, 46(10):3073-3076.
Abstract:
The texture of the inner layer, middle layer and outer layer of a cold rolled TA18 alloy tube were investigated and analyzed by means of X-ray diffraction technique. Correspondingly, contractile strain ratio (CSR), which can relate the texture to mechanical property anisotropy of a tube, was also tested. The experimental results show that texture intensity through the tube wall exist big gradient on the tube, directed by the peak value of orientation density of the orientation distribution function(ODF), and the variation gradient is over 17%, especially, texture types are different greatly among the layers. Measuring the texture of the middle layer by the method of thinning and flattening ,we discovered that although texture intensity was high for this tube,its CSR is only 0.95,less than the use standard of 1.3. The reason is due to that the texture is not uniform along the tube wall, there exists favorable texture in radial direction and negative texture in tangential direction, and strong negative texture leads to deterioration of the mechanical property. Confirming the distribution of texture along the tube wall can provide reference for forecasting and improving mechanical properties of the tube, and help to optimize the production process.
The texture of the inner layer, middle layer and outer layer of a cold rolled TA18 alloy tube were investigated and analyzed by means of X-ray diffraction technique. Correspondingly, contractile strain ratio (CSR), which can relate the texture to mechanical property anisotropy of a tube, was also tested. The experimental results show that texture intensity through the tube wall exist big gradient on the tube, directed by the peak value of orientation density of the orientation distribution function(ODF), and the variation gradient is over 17%, especially, texture types are different greatly among the layers. Measuring the texture of the middle layer by the method of thinning and flattening ,we discovered that although texture intensity was high for this tube,its CSR is only 0.95,less than the use standard of 1.3. The reason is due to that the texture is not uniform along the tube wall, there exists favorable texture in radial direction and negative texture in tangential direction, and strong negative texture leads to deterioration of the mechanical property. Confirming the distribution of texture along the tube wall can provide reference for forecasting and improving mechanical properties of the tube, and help to optimize the production process.
2017, 46(10):3077-3080.
Abstract:
The densification process of lanthanum and cerium conversion film on AZ91 magnesium alloy was achieved by ammonium phosphate, and the orthogonal expemenrit was used to optimize the densification process. The properties of the film were investigated by scanning electronic microscopy (SEM), X-ray diffractometer (XRD) and electrochemical methods. The results reveal that the treatment temperature was 50 ℃, (NH4)3PO4 mass concentration was 5%, densification of time was 4 min under the optimal treatment techniques. The SEM results show that after the densification of the rare earth conversion film, cracks in the films decreased significantly, and the denseness of the conversion coatings was improved. Results of XRD analysis indicated that the dual rare-earth conversion film with densification process are composed of rare earth oxides and hydrated hydroxides and phosphates and magnesium oxide . The electrochemical results show that the corrosion resistance of the conversion film is strengthened. High temperature oxidation test show that Lanthanum and Cerium conversion film with densification process is better than the film without densification process.
The densification process of lanthanum and cerium conversion film on AZ91 magnesium alloy was achieved by ammonium phosphate, and the orthogonal expemenrit was used to optimize the densification process. The properties of the film were investigated by scanning electronic microscopy (SEM), X-ray diffractometer (XRD) and electrochemical methods. The results reveal that the treatment temperature was 50 ℃, (NH4)3PO4 mass concentration was 5%, densification of time was 4 min under the optimal treatment techniques. The SEM results show that after the densification of the rare earth conversion film, cracks in the films decreased significantly, and the denseness of the conversion coatings was improved. Results of XRD analysis indicated that the dual rare-earth conversion film with densification process are composed of rare earth oxides and hydrated hydroxides and phosphates and magnesium oxide . The electrochemical results show that the corrosion resistance of the conversion film is strengthened. High temperature oxidation test show that Lanthanum and Cerium conversion film with densification process is better than the film without densification process.
2017, 46(10):3081-3090.
Abstract:
In order to improve the protective capability of spacecraft shielding configuration for hypervelocity impact of space debris, the Whipple-based shield configuration within the thin-plate bumpers of TiB2-based ceramic composites were manufacture(i.e. the monolayer bumper of ceramic plate, the double-layer bumper of ceramic/metal plate), the hypervelocity impact experiments were carried out on two-stage light-gas gun to compare the above novel bumpers with the typical aluminum alloy bumper under the impact velocity of 2.88 km/s ~7.32 km/s. The perforation characteristics of front bumper, the damage characteristics of rear wall and the structural characteristics of debris could were studied by combining the SEM fracture morphology and EDS elements distribution, especially, the relationship among the material properties and structure features of various bumpers, the formation process of debris clouds, the cratering mechanics of rear wall was discussed seriously. The study results showed that the monolayer ceramic bumper can effectively smash the projectile to smaller pieces in debris cloud, due to the impact kinetic energy of projectile fragments was distributed into the smaller particles of expanded debris cloud, the protective capability of the monolayer ceramic bumper exceed the typical aluminum alloy with equal areal density, moreover, the protective capability of the monolayer ceramic bumper was obviously promoted with the increasing impact velocity. On the other hand, for the double-layer ceramic/metal bumper, due to the difference in acoustic impedance between the ceramic and alumilun, the impact wace could cause the serious fracture in front ceramic plate as well as the curling deformation of rear aluminum plate, and the damge degree of ceramic/metal bumper increased in higher impact velocity. Because of the larger impact fragments and the smaller expanding bubble of the debris cloud, the protective capability of the double-layer ceramic/metal bumper is worse than the traditional aluminum bumper on the contrary. These primary results provide the theoretical and technological sopports for the space shielding application of TiB2-based ceramic composites.
In order to improve the protective capability of spacecraft shielding configuration for hypervelocity impact of space debris, the Whipple-based shield configuration within the thin-plate bumpers of TiB2-based ceramic composites were manufacture(i.e. the monolayer bumper of ceramic plate, the double-layer bumper of ceramic/metal plate), the hypervelocity impact experiments were carried out on two-stage light-gas gun to compare the above novel bumpers with the typical aluminum alloy bumper under the impact velocity of 2.88 km/s ~7.32 km/s. The perforation characteristics of front bumper, the damage characteristics of rear wall and the structural characteristics of debris could were studied by combining the SEM fracture morphology and EDS elements distribution, especially, the relationship among the material properties and structure features of various bumpers, the formation process of debris clouds, the cratering mechanics of rear wall was discussed seriously. The study results showed that the monolayer ceramic bumper can effectively smash the projectile to smaller pieces in debris cloud, due to the impact kinetic energy of projectile fragments was distributed into the smaller particles of expanded debris cloud, the protective capability of the monolayer ceramic bumper exceed the typical aluminum alloy with equal areal density, moreover, the protective capability of the monolayer ceramic bumper was obviously promoted with the increasing impact velocity. On the other hand, for the double-layer ceramic/metal bumper, due to the difference in acoustic impedance between the ceramic and alumilun, the impact wace could cause the serious fracture in front ceramic plate as well as the curling deformation of rear aluminum plate, and the damge degree of ceramic/metal bumper increased in higher impact velocity. Because of the larger impact fragments and the smaller expanding bubble of the debris cloud, the protective capability of the double-layer ceramic/metal bumper is worse than the traditional aluminum bumper on the contrary. These primary results provide the theoretical and technological sopports for the space shielding application of TiB2-based ceramic composites.
2017, 46(10):3091-3097.
Abstract:
Based on TGZM (temperature gradient zone melting) effect ,experiments on Co-87.9wt%Sb alloy consisting of melting followed by thermal stabilization ranging from 20min,2h,4h and quenching were carried out in a directional solidification apparatus, after which the solidified phases and the composition distribution were researched. The results showed that, under the temperature gradient, there exists a mushy zone between the complete liquid zone and the non-melted solid zone. Along the direction of the temperature gradient, the mushy zone of Co-87.9wt%Sb alloy is divided into three parts including (CoSb3+L),(CoSb2+L) and (CoSb+L). Due to TGZM effect, the volume fraction of the liquid phase in the mushy zone gradually decreases and the interface between the mushy zone and the complete liquid zone moves towards the low-temperature zone as thermal stabilization time increases. According to the composition distribution of the mushy zone, after thermal stabilization, the solute concentration obviously deviates from the initial concentration of Co-87.9wt%Sb alloy which is smaller than that of the complete liquid zone. Theoretical analysis and computation explain the above experimental observations. After 4h thermal stabilization, the volume fraction of CoSb3 in (CoSb3+L) of the mushy zone increases significantly up to 98.8%, which shows that it is feasible to prepare CoSb3 material via TGZM effect.
Based on TGZM (temperature gradient zone melting) effect ,experiments on Co-87.9wt%Sb alloy consisting of melting followed by thermal stabilization ranging from 20min,2h,4h and quenching were carried out in a directional solidification apparatus, after which the solidified phases and the composition distribution were researched. The results showed that, under the temperature gradient, there exists a mushy zone between the complete liquid zone and the non-melted solid zone. Along the direction of the temperature gradient, the mushy zone of Co-87.9wt%Sb alloy is divided into three parts including (CoSb3+L),(CoSb2+L) and (CoSb+L). Due to TGZM effect, the volume fraction of the liquid phase in the mushy zone gradually decreases and the interface between the mushy zone and the complete liquid zone moves towards the low-temperature zone as thermal stabilization time increases. According to the composition distribution of the mushy zone, after thermal stabilization, the solute concentration obviously deviates from the initial concentration of Co-87.9wt%Sb alloy which is smaller than that of the complete liquid zone. Theoretical analysis and computation explain the above experimental observations. After 4h thermal stabilization, the volume fraction of CoSb3 in (CoSb3+L) of the mushy zone increases significantly up to 98.8%, which shows that it is feasible to prepare CoSb3 material via TGZM effect.
2017, 46(10):3098-3104.
Abstract:
Metal surface corrosion and wear can be improved by micro-arc oxidation. The micro-arc oxidation coatings commonly exhibited porous structure, which is considered to be main reason for failure of corrosion resistance and high temperature oxidation resistance. Arsing of that, in this paper, the corrosion resistant properties of micro-arc oxidated coatings was improved by self-sealing microstructure through an applied electric field. The relationship between the porous structure of the oxidation coatings and corrosion was investgated by microstructure anylisis. Meanwhile, regularity relations of colloid motion-potential-porous structure during sealing process was discussed and the corrosion resistance of the coatings after self-sealing was evaluated by electrochemical corrosion test. The main results showed that the porous structure of the coatings is the channel corrosive medium, and corrosion resistance can be improved by the self-sealing. In addition, corrosion resistance exhibited significant dependence on porosity, composition and morphology of sealings. It is known from this paper, the corrosion resistance can be improved by self-sealing microstructure obtained by applied electric field.
Metal surface corrosion and wear can be improved by micro-arc oxidation. The micro-arc oxidation coatings commonly exhibited porous structure, which is considered to be main reason for failure of corrosion resistance and high temperature oxidation resistance. Arsing of that, in this paper, the corrosion resistant properties of micro-arc oxidated coatings was improved by self-sealing microstructure through an applied electric field. The relationship between the porous structure of the oxidation coatings and corrosion was investgated by microstructure anylisis. Meanwhile, regularity relations of colloid motion-potential-porous structure during sealing process was discussed and the corrosion resistance of the coatings after self-sealing was evaluated by electrochemical corrosion test. The main results showed that the porous structure of the coatings is the channel corrosive medium, and corrosion resistance can be improved by the self-sealing. In addition, corrosion resistance exhibited significant dependence on porosity, composition and morphology of sealings. It is known from this paper, the corrosion resistance can be improved by self-sealing microstructure obtained by applied electric field.
2017, 46(10):3105-3110.
Abstract:
The incipient melting process of a B bearing third generation single crystal superalloy was investigated by Thermol-Calc software. The simulation data was obtained by EPMA. The results show that the incipient melting phase was M2B and the incipient melting temperature was 1265 ℃, which is significantly lower than the melting temperature of eutectic (1352 ℃) obtained by DSC. The dissolution of γ/γ′ eutectics was studied by SEM. It was indicated that more time and higher temperature were necessary to dissolve the coarsen γ′ in eutectics than mosaic like eutectics and fan like eutectics. The sharp of incipient melting region was round. Homogenous nucleation could be found in incipient melting region due to the fast cooling rate of air cooling. The resolidification structure owned mosaic like eutectics and fan like eutectics which were dissolved in the early stage of solution heat treatment.
The incipient melting process of a B bearing third generation single crystal superalloy was investigated by Thermol-Calc software. The simulation data was obtained by EPMA. The results show that the incipient melting phase was M2B and the incipient melting temperature was 1265 ℃, which is significantly lower than the melting temperature of eutectic (1352 ℃) obtained by DSC. The dissolution of γ/γ′ eutectics was studied by SEM. It was indicated that more time and higher temperature were necessary to dissolve the coarsen γ′ in eutectics than mosaic like eutectics and fan like eutectics. The sharp of incipient melting region was round. Homogenous nucleation could be found in incipient melting region due to the fast cooling rate of air cooling. The resolidification structure owned mosaic like eutectics and fan like eutectics which were dissolved in the early stage of solution heat treatment.
2017, 46(10):3111-3116.
Abstract:
Magnesium and magnesium alloys have attracted increasing attention as implant materials due to their suitable mechanical properties with bones, good biocompatibility and biodegradability in physiological environment. The addition of bioceramic particles into magnesium alloy can adjust mechanical properties as well as the corrosion properties to meet the requirements service performance. In this paper, 1HA/Mg-3Zn-0.2Ca composities were fabricated by means of melt high shearing technology combined with following hot extrusion. Effects of heat treatment on microstructures, mechanical and corrosion resistance properties were investigated. The results indicated that after solid solution treatment (T4 treatment), the amounts of secondary phases in 1HA/Mg-3Zn-0.2Ca composite decreases, grain size became larger, yield strength decreased, the elongation and the corrosion resistance increased. However, the corrosion resistance show a decreasing trend as the solid solution treatment time exceeded 3h , which was attributed to grain size is overlarge. Aging treatment after solid solution, the yield strength increased and the corrosion resistance was not changed obviously. Hence, the as-extruded 1HA/Mg-3Zn-0.2Ca composite can be improved the corrosion resistance and elongation by suitable solid solution and aging heat treatment.
Magnesium and magnesium alloys have attracted increasing attention as implant materials due to their suitable mechanical properties with bones, good biocompatibility and biodegradability in physiological environment. The addition of bioceramic particles into magnesium alloy can adjust mechanical properties as well as the corrosion properties to meet the requirements service performance. In this paper, 1HA/Mg-3Zn-0.2Ca composities were fabricated by means of melt high shearing technology combined with following hot extrusion. Effects of heat treatment on microstructures, mechanical and corrosion resistance properties were investigated. The results indicated that after solid solution treatment (T4 treatment), the amounts of secondary phases in 1HA/Mg-3Zn-0.2Ca composite decreases, grain size became larger, yield strength decreased, the elongation and the corrosion resistance increased. However, the corrosion resistance show a decreasing trend as the solid solution treatment time exceeded 3h , which was attributed to grain size is overlarge. Aging treatment after solid solution, the yield strength increased and the corrosion resistance was not changed obviously. Hence, the as-extruded 1HA/Mg-3Zn-0.2Ca composite can be improved the corrosion resistance and elongation by suitable solid solution and aging heat treatment.
2017, 46(10):3117-3122.
Abstract:
Palladium is an important functional material in tritium treating technology, tritium decay and its product,helium-3 will decrease the properties of hydrogen storage of palladium. The PcT curves of absorbing/desorbing protium and deuterium were measured by the varying temperature method for aged palladium after 1.6 years tritium storage, the experimental results of fresh sponge palladium were provided for comparison in this work, furthermore, thermodynamics of the aged palladium absorbing/desorbing protium and deuterium was analyzed. Comparing with the fresh palladium, tritium aging compel a phase zone to shift right, decreases the plateau pressures of aged Pd-H and Pd-D systems as narrowing down the scope of the plateau pressures, further analyzing shows that the tritium aging weakens the hysteresis effect of palladium absorbing/desorbing hydrogen, affects the enthalpy and entropy changes of the formation of palladium hydride.
Palladium is an important functional material in tritium treating technology, tritium decay and its product,helium-3 will decrease the properties of hydrogen storage of palladium. The PcT curves of absorbing/desorbing protium and deuterium were measured by the varying temperature method for aged palladium after 1.6 years tritium storage, the experimental results of fresh sponge palladium were provided for comparison in this work, furthermore, thermodynamics of the aged palladium absorbing/desorbing protium and deuterium was analyzed. Comparing with the fresh palladium, tritium aging compel a phase zone to shift right, decreases the plateau pressures of aged Pd-H and Pd-D systems as narrowing down the scope of the plateau pressures, further analyzing shows that the tritium aging weakens the hysteresis effect of palladium absorbing/desorbing hydrogen, affects the enthalpy and entropy changes of the formation of palladium hydride.
60 Study on the preparation of spherical molybdenum powder by spray drying and microwave calcination
2017, 46(10):3123-3128.
Abstract:
In this paper ,the molybdenum powder of spherical, micron size, large specific surface area and good dispersion was prepared by spray drying and microwave calcination, and ammonium paramolybdate (GR pure) as raw material. The effect of spray drying and heating rate of microwave calcination on the surface morphology, particle size and specific surface area of the final Mo powder was studied. Research results show that the Mo precursor powder of spherical, micron size and good dispersion was prepared by controlling parameters. The micro morphology of the final Mo powder is affected by the heating rate. When the heating rate is low, the Mo powder is broken more serious and had a small amount of aggregation . The Mo powder with well spherical and good dispersion was prepared, when the heating rate is becoming higher. The heating rate also directly affects the average particle size and specific surface area. The lower the heating rate, the smaller the average particle size, and the larger the specific surface area. The average particle size is becoming bigger and the specific surface area is becoming smaller when the heating rate is higher.
In this paper ,the molybdenum powder of spherical, micron size, large specific surface area and good dispersion was prepared by spray drying and microwave calcination, and ammonium paramolybdate (GR pure) as raw material. The effect of spray drying and heating rate of microwave calcination on the surface morphology, particle size and specific surface area of the final Mo powder was studied. Research results show that the Mo precursor powder of spherical, micron size and good dispersion was prepared by controlling parameters. The micro morphology of the final Mo powder is affected by the heating rate. When the heating rate is low, the Mo powder is broken more serious and had a small amount of aggregation . The Mo powder with well spherical and good dispersion was prepared, when the heating rate is becoming higher. The heating rate also directly affects the average particle size and specific surface area. The lower the heating rate, the smaller the average particle size, and the larger the specific surface area. The average particle size is becoming bigger and the specific surface area is becoming smaller when the heating rate is higher.
2017, 46(10):3129-3134.
Abstract:
To improve the service performance of metal parts in harsh marine environment, the effects of SiC on the corrosion and wear resistance of the Ni-W Alloys were investigated by scanning electron microscopy (SEM), energy spectrum analysis (EDS) and X ray diffraction (XRD). The influences of SiC nanoparticles on Ni-W composite electrodeposition process and the electrochemical corrosion properties of Ni-W/SiC composite coatings were studied by EIS and Tafel methods. The results show that SiC which pretreated were uniformly dispersed in compact Ni-W/SiC coating which can effectively improve the hardness and wear resistance at the same time. The addition of W6+ refine the grain size of the Ni coating, reduce the porosity, transform some structure to amorphous and improve the corrosion resistance. SiC nano particles can promote the nucleation and growth of Ni-W alloy and improve the hardness of the alloys. Compared with Ni-W alloys, with the wear resistance increased and porosity decreased, Ni-W/SiC alloys have excellent corrosion resistance and wear resistance. Ni-W/SiC alloys also have better abrasion and corrosion resistance than Ni-W alloy, and can provide comprehensive service performance for marine parts under the influence of multifactor interaction in seawater environment. It has a good application prospect in the field of marine engineering protection.
To improve the service performance of metal parts in harsh marine environment, the effects of SiC on the corrosion and wear resistance of the Ni-W Alloys were investigated by scanning electron microscopy (SEM), energy spectrum analysis (EDS) and X ray diffraction (XRD). The influences of SiC nanoparticles on Ni-W composite electrodeposition process and the electrochemical corrosion properties of Ni-W/SiC composite coatings were studied by EIS and Tafel methods. The results show that SiC which pretreated were uniformly dispersed in compact Ni-W/SiC coating which can effectively improve the hardness and wear resistance at the same time. The addition of W6+ refine the grain size of the Ni coating, reduce the porosity, transform some structure to amorphous and improve the corrosion resistance. SiC nano particles can promote the nucleation and growth of Ni-W alloy and improve the hardness of the alloys. Compared with Ni-W alloys, with the wear resistance increased and porosity decreased, Ni-W/SiC alloys have excellent corrosion resistance and wear resistance. Ni-W/SiC alloys also have better abrasion and corrosion resistance than Ni-W alloy, and can provide comprehensive service performance for marine parts under the influence of multifactor interaction in seawater environment. It has a good application prospect in the field of marine engineering protection.
Lv Dongfeng
,
Bu Jinglong
,
Wei Hengyong
,
Cui Yi
,
Ni Jie
,
Liu Pan
,
Liu Huixing
,
Wei Yingna
,
Zhang Lifang
2017, 46(10):3135-3140.
Abstract:
The porous titanium nitride fibers were prepared by electrospinning combined with reduction-nitride process. The structural information of the prepared fibers can be characterized by XRD, SEM, TEM and BET. And the electrochemical feature was characterized by cyclic voltammetry and charge-discharge measurements. The results showed that the synthesized TiN continuous fiber was cubic TiN phase, and there existed abundant mesoporous structure. The specific surface area of fiber was 21.55 m2/g. The CV curves at different scan rate were similar to the rectangle. The specific capacitance was 24.03 F/g when the current density was 20 mA/g. When the current density was 50 mA/g, the specific capacitance remained above 90 % after charge-discharge measurement for 4500 times. Moreover, the power density was 0.02 kW/kg and the energy density was 3.3 Wh/kg. In summary, the porous TiN fibers have great potential application in the field of super capacitor.
The porous titanium nitride fibers were prepared by electrospinning combined with reduction-nitride process. The structural information of the prepared fibers can be characterized by XRD, SEM, TEM and BET. And the electrochemical feature was characterized by cyclic voltammetry and charge-discharge measurements. The results showed that the synthesized TiN continuous fiber was cubic TiN phase, and there existed abundant mesoporous structure. The specific surface area of fiber was 21.55 m2/g. The CV curves at different scan rate were similar to the rectangle. The specific capacitance was 24.03 F/g when the current density was 20 mA/g. When the current density was 50 mA/g, the specific capacitance remained above 90 % after charge-discharge measurement for 4500 times. Moreover, the power density was 0.02 kW/kg and the energy density was 3.3 Wh/kg. In summary, the porous TiN fibers have great potential application in the field of super capacitor.
2017, 46(10):3141-3145.
Abstract:
The research of cellular structure evolution of aluminum foam sandwich that made by the pack rolling/powder metallurgy foaming process has been done using SR-CT, and also the variation of porosity of aluminum foam and occurring of oversize connected pores have been analyzed. The results show that the cellular structure can be observed clearly during the appearing and growing stages by using SR-CT with the spatial resolution of micrometer. The bubble hole that similar to spalttupfel which is perpendicular to the rolling direction generated from 15 to 30 seconds, and then it is an obvious merge at about 45 seconds. With time going on, the large size connected hole form more easily. The porosity of aluminum foam grow quickly at the stage of appearing and merging process. So in order to gain excellent foaming structure of sandwich layer, the reduction of the reunion of foaming agent during mixing material and improvement of powder density of the sandwich layer is necessary.
The research of cellular structure evolution of aluminum foam sandwich that made by the pack rolling/powder metallurgy foaming process has been done using SR-CT, and also the variation of porosity of aluminum foam and occurring of oversize connected pores have been analyzed. The results show that the cellular structure can be observed clearly during the appearing and growing stages by using SR-CT with the spatial resolution of micrometer. The bubble hole that similar to spalttupfel which is perpendicular to the rolling direction generated from 15 to 30 seconds, and then it is an obvious merge at about 45 seconds. With time going on, the large size connected hole form more easily. The porosity of aluminum foam grow quickly at the stage of appearing and merging process. So in order to gain excellent foaming structure of sandwich layer, the reduction of the reunion of foaming agent during mixing material and improvement of powder density of the sandwich layer is necessary.
2017, 46(10):3146-3150.
Abstract:
Adopting vacuum induction melting and step copper mould casting method, non-equilibrium solidified AZ91 magnesium alloy containing SiC particle was fabricated. Then, the microstructure evolution regularity of sub-rapid solidified alloys was revealed considering the effects of heterogeneous particle and cooling rate. In the condition of same inner diameter of copper mould, the addition of SiC particle is beneficial for the refinement of magnesium alloy. After solid solution treatment at 400℃, the β-Mg17Al12 phase at the grain boundary disappears gradually, accompanied by the morphology transition of primary α-Mg from fine granular to polygonal structure. Due to the pinning effect of SiC for grain growth at higher temperature, the initial refined microstructure can be saved after 2h and the whole grain size distribution becomes homogeneous. With decreasing the diameter of copper mould, the cooling rate during solidification is increased and the grain refinement is enhanced as well. As for the specimen with the addition of 2wt% SiC and diameter of 2mm, maximum hardness with the value of 142Hv can be obtained, which is increased by 87% in comparison with the as-cast alloy.
Adopting vacuum induction melting and step copper mould casting method, non-equilibrium solidified AZ91 magnesium alloy containing SiC particle was fabricated. Then, the microstructure evolution regularity of sub-rapid solidified alloys was revealed considering the effects of heterogeneous particle and cooling rate. In the condition of same inner diameter of copper mould, the addition of SiC particle is beneficial for the refinement of magnesium alloy. After solid solution treatment at 400℃, the β-Mg17Al12 phase at the grain boundary disappears gradually, accompanied by the morphology transition of primary α-Mg from fine granular to polygonal structure. Due to the pinning effect of SiC for grain growth at higher temperature, the initial refined microstructure can be saved after 2h and the whole grain size distribution becomes homogeneous. With decreasing the diameter of copper mould, the cooling rate during solidification is increased and the grain refinement is enhanced as well. As for the specimen with the addition of 2wt% SiC and diameter of 2mm, maximum hardness with the value of 142Hv can be obtained, which is increased by 87% in comparison with the as-cast alloy.
2017, 46(10):3151-3155.
Abstract:
The effect of indium ion concentration, current density and continuous electrolysis time on the purity and size of the powder by electrolysis process was studied. The results show that：Continuous electrolysis time is longer, the larger sizes of the powder were obtained when the electric parameters are: NaCl concentration is 80g/L, polar distance is 5 cm, thiourea concentration is 0.3 g/L, gelatin concentration is 0.5 g/l, pH = 2.5, Polyvinyl ketone(PVP) is 0.2 g/L. When the current density is 130 A/m2, the particle size of the powder is the smallest, and the purity is the highest. The effect of In3+ concentration on the particle size is the least, but the influence on the purity is the most. Under the conditions of process parameters above and In3+ concentration of 30 g/L, the current density of 130 A/cm2, electrolytic for 1h, the particle size of less than 100 μm indium powder were obtained, which the particle size of less than 30 μm accounted for 75%.
The effect of indium ion concentration, current density and continuous electrolysis time on the purity and size of the powder by electrolysis process was studied. The results show that：Continuous electrolysis time is longer, the larger sizes of the powder were obtained when the electric parameters are: NaCl concentration is 80g/L, polar distance is 5 cm, thiourea concentration is 0.3 g/L, gelatin concentration is 0.5 g/l, pH = 2.5, Polyvinyl ketone(PVP) is 0.2 g/L. When the current density is 130 A/m2, the particle size of the powder is the smallest, and the purity is the highest. The effect of In3+ concentration on the particle size is the least, but the influence on the purity is the most. Under the conditions of process parameters above and In3+ concentration of 30 g/L, the current density of 130 A/cm2, electrolytic for 1h, the particle size of less than 100 μm indium powder were obtained, which the particle size of less than 30 μm accounted for 75%.
2017, 46(10):3156-3159.
Abstract:
This paper addresses the issue of transient liquid phase diffusion bonding of pure titanium to 304 stainless steel using aluminum interlayer, at the temperature of 650 ℃ for 2 h under 2 MPa load in vacuum. Then the result was compared with the case of 550 ℃ and 600 ℃. The microstructures, chemical compositions and reaction products of the transition joints were revealed in SEM, EDS and XRD, respectively. The experimental results has shown that, the position of the transient liquid phase diffusion bonding interface is different from that of the conventional thermal diffusion, and aluminum play a mid sole element to prevent iron diffusion to titanium master alloys forming brittle intermetallic phase Fe-Ti. This paper introduces a new technique of Ti-Al-304 stainless steel composite plate diffusion bonding.
This paper addresses the issue of transient liquid phase diffusion bonding of pure titanium to 304 stainless steel using aluminum interlayer, at the temperature of 650 ℃ for 2 h under 2 MPa load in vacuum. Then the result was compared with the case of 550 ℃ and 600 ℃. The microstructures, chemical compositions and reaction products of the transition joints were revealed in SEM, EDS and XRD, respectively. The experimental results has shown that, the position of the transient liquid phase diffusion bonding interface is different from that of the conventional thermal diffusion, and aluminum play a mid sole element to prevent iron diffusion to titanium master alloys forming brittle intermetallic phase Fe-Ti. This paper introduces a new technique of Ti-Al-304 stainless steel composite plate diffusion bonding.
2017, 46(10):3160-3168.
Abstract:
Metal additive manufacturing (MAM) technology can realize the large-and-complex parts of the titanium alloy with high performance solid free forming, is widely used in aviation, aerospace, power and energy industry in recent years. Based on the relationship between microstructure and mechanical properties, this review describes the as-deposited, heat-treated microstructure and texture in AM Ti-6Al-4V alloy, and tensile and fatigue properties. In addition, we point out the key issues in MAM Ti-6Al-4V alloy and the developing trends in AM Ti-6Al-4V alloy.
Metal additive manufacturing (MAM) technology can realize the large-and-complex parts of the titanium alloy with high performance solid free forming, is widely used in aviation, aerospace, power and energy industry in recent years. Based on the relationship between microstructure and mechanical properties, this review describes the as-deposited, heat-treated microstructure and texture in AM Ti-6Al-4V alloy, and tensile and fatigue properties. In addition, we point out the key issues in MAM Ti-6Al-4V alloy and the developing trends in AM Ti-6Al-4V alloy.
2017, 46(10):2781-2784.
Abstract:
Anatase TiO2 thin films were grown on quartz substrates by RF magnetron sputtering. Metal-semiconductor-metal (MSM) detectors with Ag IDT electrodes were then fabricated. The measurement of the I-V characteristics for the detectors shows good ohmic contact. It was found that the thickness of TiO2 layer had an obvious effect on the photoelectronic properties. When TiO2 film thickness is 197 nm, the photocurrent is nearly 2.5 orders of magnitude higher than the dark current and the photoresponse in ultraviolet region is nearly 2 orders of magnitude higher than in visible light region. The high sensitivity and visible blind properties of the obtained devices indicate their potential application as UV detectors with high efficiency and low cost.
Anatase TiO2 thin films were grown on quartz substrates by RF magnetron sputtering. Metal-semiconductor-metal (MSM) detectors with Ag IDT electrodes were then fabricated. The measurement of the I-V characteristics for the detectors shows good ohmic contact. It was found that the thickness of TiO2 layer had an obvious effect on the photoelectronic properties. When TiO2 film thickness is 197 nm, the photocurrent is nearly 2.5 orders of magnitude higher than the dark current and the photoresponse in ultraviolet region is nearly 2 orders of magnitude higher than in visible light region. The high sensitivity and visible blind properties of the obtained devices indicate their potential application as UV detectors with high efficiency and low cost.
2017, 46(10):2831-2836.
Abstract:
Isothermal compression tests of 25vol% B4Cp/2009Al composite have been carried out in the temperature range from 300℃ to 500℃ and the strain rate range from 0.001s-1 to 1s-1. The results show that high-temperature flow stress of the composite decreases with the increase of deformation temperature and the decrease of strain rate. The flow stress has been corrected by friction and the friction corrected stress is lower than experimental values. The influence of friction becomes more obvious with decreasing temperature and increasing strain rate. Then a constitutive equation considering the effect of stain on material constants (i.e. α, n, Q and A) is developed on the basis of Arrhenius type equation. Compared with the experimental results, the flow stress calculated by the constitutive equation possesses a high precision with the correlation coefficient of 0.992. Higher temperature and lower strain rate is beneficial for hot deformation of B4Cp/2009Al composite.
Isothermal compression tests of 25vol% B4Cp/2009Al composite have been carried out in the temperature range from 300℃ to 500℃ and the strain rate range from 0.001s-1 to 1s-1. The results show that high-temperature flow stress of the composite decreases with the increase of deformation temperature and the decrease of strain rate. The flow stress has been corrected by friction and the friction corrected stress is lower than experimental values. The influence of friction becomes more obvious with decreasing temperature and increasing strain rate. Then a constitutive equation considering the effect of stain on material constants (i.e. α, n, Q and A) is developed on the basis of Arrhenius type equation. Compared with the experimental results, the flow stress calculated by the constitutive equation possesses a high precision with the correlation coefficient of 0.992. Higher temperature and lower strain rate is beneficial for hot deformation of B4Cp/2009Al composite.
2017, 46(10):2987-2992.
Abstract:
Pure molybdenum powder was successfully directly compacted into the dense body material by high-pressure torsion at 350℃. The effects of HPT on pore closure and performance strengthening of the powder particle were investigated by optical telescope, microhardness-testing device, scanning electronic telescope and X-ray diffractometer. The results indicate that the molybdenum powder mechanical mesh each other by particles movement and deformation under shear force, at this time the interface bonding performance, the large chain pores in particles were welded effectively after high-pressure torsion. In the HPT process the crystal size decrease from 59.8nm to 46.9nm, the micro strain increases from 1.04′10-4to 1.12′10-3. The lattice defects caused by grain refinement and micro strain can promote dislocation multiplication and tangling to strengthen the matrixmethod.
Pure molybdenum powder was successfully directly compacted into the dense body material by high-pressure torsion at 350℃. The effects of HPT on pore closure and performance strengthening of the powder particle were investigated by optical telescope, microhardness-testing device, scanning electronic telescope and X-ray diffractometer. The results indicate that the molybdenum powder mechanical mesh each other by particles movement and deformation under shear force, at this time the interface bonding performance, the large chain pores in particles were welded effectively after high-pressure torsion. In the HPT process the crystal size decrease from 59.8nm to 46.9nm, the micro strain increases from 1.04′10-4to 1.12′10-3. The lattice defects caused by grain refinement and micro strain can promote dislocation multiplication and tangling to strengthen the matrixmethod.
