Volume 45,Issue 10,2016 Table of Contents
2016, 45(10):2473-2479.
Abstract:
The precipitation behavior of secondary phase particles (SPPs) was investigated systematically in Zr-1Nb-0.01Cu alloy produced by various processing technologies. The results show that with the decrease of cold rolling and annealing steps, intermediate annealing temperatures, final annealing temperatures and time, the average size of SPPs decrease accordingly. The β-Zr phase formed at the intermediate annealing temperature (higher than 640 °C) is hard to dissolve in the matrix after final annealing treatment. During long-time final annealing process, the SPPs with smaller size coalesce into larger particles by diffusion through the matrix gradually because of Ostwald ripening mechanism. It shows that the decrease of intermediate annealing temperature is more effective than the other processing technologies for minimizing the size of SPPs. The average particle size which is smaller than 50nm can be achieved by low intermediate/final annealing temperature (≤520°C) or short annealing time (≤2 hours) treatment. The investigations in the present paper are very meaningful to control the SPPs in Zr-Nb based alloys.
The precipitation behavior of secondary phase particles (SPPs) was investigated systematically in Zr-1Nb-0.01Cu alloy produced by various processing technologies. The results show that with the decrease of cold rolling and annealing steps, intermediate annealing temperatures, final annealing temperatures and time, the average size of SPPs decrease accordingly. The β-Zr phase formed at the intermediate annealing temperature (higher than 640 °C) is hard to dissolve in the matrix after final annealing treatment. During long-time final annealing process, the SPPs with smaller size coalesce into larger particles by diffusion through the matrix gradually because of Ostwald ripening mechanism. It shows that the decrease of intermediate annealing temperature is more effective than the other processing technologies for minimizing the size of SPPs. The average particle size which is smaller than 50nm can be achieved by low intermediate/final annealing temperature (≤520°C) or short annealing time (≤2 hours) treatment. The investigations in the present paper are very meaningful to control the SPPs in Zr-Nb based alloys.
2016, 45(10):2480-2484.
Abstract:
The spheroidizing behavior of the lamellar Al8CeCu4 phase in the Al-14Cu-7Ce alloy annealed at elevated temperatures was investigated by microstructural observation, hardness testing and theoretical calculation. With increasing the annealing temperature, the spheroidizing process of the Al8CeCu4 phase was accelerated. The controlling element for the spheroidizing process was determined being Ce by theoretical calculation using the general rate equation. Microstructure observation indicated that the spheroidizing process of the Al8CeCu4 phase included two successive parts, i.e., the curved lamella breaking into long rods by Gibbs-Thompson effect and then the rods separating into spherical particles further by Rayleigh’s capillary induced perturbation mechanism.
The spheroidizing behavior of the lamellar Al8CeCu4 phase in the Al-14Cu-7Ce alloy annealed at elevated temperatures was investigated by microstructural observation, hardness testing and theoretical calculation. With increasing the annealing temperature, the spheroidizing process of the Al8CeCu4 phase was accelerated. The controlling element for the spheroidizing process was determined being Ce by theoretical calculation using the general rate equation. Microstructure observation indicated that the spheroidizing process of the Al8CeCu4 phase included two successive parts, i.e., the curved lamella breaking into long rods by Gibbs-Thompson effect and then the rods separating into spherical particles further by Rayleigh’s capillary induced perturbation mechanism.
2016, 45(10):2485-2491.
Abstract:
Gravity-pouring of a TiAlNb alloy from an induction skull melting (ISM) furnace into a ceramic shell mould has been carried out in this paper. Microstructure and gas defects were examined by employing scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) analysis. It has been found that oxide films existed in the form of bubbles and porosity, and acted as defects’ heterogeneous nucleation sites. The bubbles consisted of entrained and precipitable ones, while the porosity consisted of layer and centerline ones. The diameter of casting bars, mould temperature and the partial pressure of argon had an effect on the formation of gas defects.
Gravity-pouring of a TiAlNb alloy from an induction skull melting (ISM) furnace into a ceramic shell mould has been carried out in this paper. Microstructure and gas defects were examined by employing scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) analysis. It has been found that oxide films existed in the form of bubbles and porosity, and acted as defects’ heterogeneous nucleation sites. The bubbles consisted of entrained and precipitable ones, while the porosity consisted of layer and centerline ones. The diameter of casting bars, mould temperature and the partial pressure of argon had an effect on the formation of gas defects.
2016, 45(10):2492-2497.
Abstract:
HVOF cermet coatings have been widely used in aviation and marine fields of key components. Those parts often serve in rigorous environment characterized with salt-fog atmosphere. In order to enhance the wear- and corrosion-resistance of those components, two kinds of cermet coating, that is WC-10Co4Cr and Cr3C2-NiCr coating, were prepared by HVOF and then their tribology properties were investigated by a reconstructive friction testing machine equipped with an artificial salt-fog spraying apparatus. As well as, similar research was performed on traditional chrome plating (Cr-plating) for contrasting. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were utilized to characterize the wear surface. The results indicated that various coatings exhibited different wear mechanisms. Cr-plating displayed mainly adhesive-wear mechanism, Cr3C2-NiCr coating displayed both adhesive-wear and abrasive-wear mechanism, while WC-10Co4Cr displayed mainly abrasive-wear mechanism. At the salt-fog atmosphere, liquid membrane was considered as a factor to reduce the friction-coefficient and wear-rate of the coatings. It was also indicatied that when the contacting pressure of the friction pair was increased, the wear-rate of Cr-plating and Cr3C2-NiCr coating are significantly enhanced, but that of WC-10Co4Cr coating is reduced at the opposite way. The phenomenon can ben ascribed to different transformation mechanism of abrasion for various coating at high contacting pressure.
HVOF cermet coatings have been widely used in aviation and marine fields of key components. Those parts often serve in rigorous environment characterized with salt-fog atmosphere. In order to enhance the wear- and corrosion-resistance of those components, two kinds of cermet coating, that is WC-10Co4Cr and Cr3C2-NiCr coating, were prepared by HVOF and then their tribology properties were investigated by a reconstructive friction testing machine equipped with an artificial salt-fog spraying apparatus. As well as, similar research was performed on traditional chrome plating (Cr-plating) for contrasting. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were utilized to characterize the wear surface. The results indicated that various coatings exhibited different wear mechanisms. Cr-plating displayed mainly adhesive-wear mechanism, Cr3C2-NiCr coating displayed both adhesive-wear and abrasive-wear mechanism, while WC-10Co4Cr displayed mainly abrasive-wear mechanism. At the salt-fog atmosphere, liquid membrane was considered as a factor to reduce the friction-coefficient and wear-rate of the coatings. It was also indicatied that when the contacting pressure of the friction pair was increased, the wear-rate of Cr-plating and Cr3C2-NiCr coating are significantly enhanced, but that of WC-10Co4Cr coating is reduced at the opposite way. The phenomenon can ben ascribed to different transformation mechanism of abrasion for various coating at high contacting pressure.
2016, 45(10):2498-2502.
Abstract:
Porous materials as a new type structure and functional materials, duo to specially structure compared with the dense materials, which given the excellent properties of materials. The powder metallurgy with space holder technique was used to prepare magnesium foam. The porosity increases from 38.90% up to 57.50%, resulting in that the elastic modulus decreases from 8.50GPa to 3.30GPa, and resulting in that the yield stress decreases from 24.90MPa to 9.40 MPa. Magnesium foam has lower yield stress and longer stress platform, so it can be used as excellent cushioning energy absorbing materials.
Porous materials as a new type structure and functional materials, duo to specially structure compared with the dense materials, which given the excellent properties of materials. The powder metallurgy with space holder technique was used to prepare magnesium foam. The porosity increases from 38.90% up to 57.50%, resulting in that the elastic modulus decreases from 8.50GPa to 3.30GPa, and resulting in that the yield stress decreases from 24.90MPa to 9.40 MPa. Magnesium foam has lower yield stress and longer stress platform, so it can be used as excellent cushioning energy absorbing materials.
2016, 45(10):2503-2508.
Abstract:
In this paper, large-scale silver nanowires with a lenghth of 30-90 μm were successfully synthesized by a polyol process. Electronically conductive adhesives (ECAs) were made by adding micro-sized silver flakes and silver nanowires to the polymer composites consisted mainly of epoxy resin, cure agent and catalyst. The volume resistivity of the ECAs was researched as a function of silver filling loading and sintering temperature. The results indicated that the volume resistivity of ECAs first decreased and then increased with the increase of fractions of silver nanowires when curing temperature at 180 0C. With the increase of curing temperature, the volume resistivity of ECAs increased. In the condition of the ECAs filled 65% silver fillers (the ratio of silver micro-sized silver flakes and silver nanowires is 55:10), the volume resistivity of ECAs reached 6.5?0-4 Ω?cm and 1.3?0-4 Ω?cm cured at 180 0C and 300 0C, respectively. The dramatic improvement in the conductivity of the ECAs is due to the low-temperature sintering of the silver nanowires at 300 0C. Effect of silver nanowires on the resistivity of ECAs was discussed in terms of the distribution and sintering behavior of silver nanowires and interaction relationship between silver nanowires and micro-sized silver flakes.
In this paper, large-scale silver nanowires with a lenghth of 30-90 μm were successfully synthesized by a polyol process. Electronically conductive adhesives (ECAs) were made by adding micro-sized silver flakes and silver nanowires to the polymer composites consisted mainly of epoxy resin, cure agent and catalyst. The volume resistivity of the ECAs was researched as a function of silver filling loading and sintering temperature. The results indicated that the volume resistivity of ECAs first decreased and then increased with the increase of fractions of silver nanowires when curing temperature at 180 0C. With the increase of curing temperature, the volume resistivity of ECAs increased. In the condition of the ECAs filled 65% silver fillers (the ratio of silver micro-sized silver flakes and silver nanowires is 55:10), the volume resistivity of ECAs reached 6.5?0-4 Ω?cm and 1.3?0-4 Ω?cm cured at 180 0C and 300 0C, respectively. The dramatic improvement in the conductivity of the ECAs is due to the low-temperature sintering of the silver nanowires at 300 0C. Effect of silver nanowires on the resistivity of ECAs was discussed in terms of the distribution and sintering behavior of silver nanowires and interaction relationship between silver nanowires and micro-sized silver flakes.
2016, 45(10):2509-2512.
Abstract:
Abstract: “Oxygen-free” Gd was fabricated by Hydrogen plasma arc melting (HPAM). The Oxygen concentration had a tendency of reduction compared with that done by Ar PAM. All these are attributable to the process of melting, especially the hydrogen atoms dissociated and activated in high temperature HPAM. An increased diffusion of oxygen in Gd-O solid solution to the surface is also believed to play an important role in removal of oxygen. The optical emission spectroscopy (OES) measurement is used to confirm the substances which were involved in the plasma like Ar I, Ar II and H I and some possible reactions. The effect of H with thermodynamic estimation is discussed in details.
Abstract: “Oxygen-free” Gd was fabricated by Hydrogen plasma arc melting (HPAM). The Oxygen concentration had a tendency of reduction compared with that done by Ar PAM. All these are attributable to the process of melting, especially the hydrogen atoms dissociated and activated in high temperature HPAM. An increased diffusion of oxygen in Gd-O solid solution to the surface is also believed to play an important role in removal of oxygen. The optical emission spectroscopy (OES) measurement is used to confirm the substances which were involved in the plasma like Ar I, Ar II and H I and some possible reactions. The effect of H with thermodynamic estimation is discussed in details.
2016, 45(10):2513-2518.
Abstract:
Wf/Cu78Al10Fe6Ni6 composite was fabricated by Cu78Al10Fe6Ni6 alloy and tungsten fiber by means of infiltration casting. Used two-stage light gas gun, Wf/Cu78Al10Fe6Ni6 composite hypervelocity projectile impacted concrete target test with the speed of 2.4 km/s was finished. Microstructure of the residual projectiles after penetration was observed with the aid of transmission electron microscope (TEM). Due to the effect of high temperature and pressure during the process of penetration, there were different microstructures existing in different zones of the residual projectiles, i.e. amorphous microstructures, recrystallization microstructures, twins, stacking faults and dislocations in order from warhead to afterbody. Matrix copper alloy melted and then rapidly solidified due to high temperature produced by projectiles during the process of impact, thus amorphous microstructures were generated. Recrystallization microstructures were generated due to rotational dynamic recrystallization of copper matrix. Twins, stacking faults and high-density dislocations were generated due to serious plastic deformation of projectiles under large dynamic loads in the process of penetration.
Wf/Cu78Al10Fe6Ni6 composite was fabricated by Cu78Al10Fe6Ni6 alloy and tungsten fiber by means of infiltration casting. Used two-stage light gas gun, Wf/Cu78Al10Fe6Ni6 composite hypervelocity projectile impacted concrete target test with the speed of 2.4 km/s was finished. Microstructure of the residual projectiles after penetration was observed with the aid of transmission electron microscope (TEM). Due to the effect of high temperature and pressure during the process of penetration, there were different microstructures existing in different zones of the residual projectiles, i.e. amorphous microstructures, recrystallization microstructures, twins, stacking faults and dislocations in order from warhead to afterbody. Matrix copper alloy melted and then rapidly solidified due to high temperature produced by projectiles during the process of impact, thus amorphous microstructures were generated. Recrystallization microstructures were generated due to rotational dynamic recrystallization of copper matrix. Twins, stacking faults and high-density dislocations were generated due to serious plastic deformation of projectiles under large dynamic loads in the process of penetration.
2016, 45(10):2519-2523.
Abstract:
Directional solidification of metal/gas eutectic (Gasar) is a novel process for fabricating porous metals with oriented pores parallel to the solidification direction. By use of the developed Gasar apparatus, lotus-type porous silver samples with different porosities have been fabricated in oxygen atmosphere. In this paper, we studied the effects of gas pressure on porosity, pore nucleation, pore size and distribution. It is concluded that the porosity and the pore size in the lotus-type porous silver were significantly affected by pressures of oxygen. The porosity increases with increasing pressure of oxygen. The average pore diameter decreases with increasing of oxygen pressure.
Directional solidification of metal/gas eutectic (Gasar) is a novel process for fabricating porous metals with oriented pores parallel to the solidification direction. By use of the developed Gasar apparatus, lotus-type porous silver samples with different porosities have been fabricated in oxygen atmosphere. In this paper, we studied the effects of gas pressure on porosity, pore nucleation, pore size and distribution. It is concluded that the porosity and the pore size in the lotus-type porous silver were significantly affected by pressures of oxygen. The porosity increases with increasing pressure of oxygen. The average pore diameter decreases with increasing of oxygen pressure.
2016, 45(10):2524-2528.
Abstract:
In this paper, a typical isotropic conductive adhesives (ICAs) composed of an epoxy-based binder containing micro-sized silver flakes was prepared and the effects of the different curing procedures on the electrical properties of the ICAs were investigated. The results showed that there is greater influence of the curing temperature on 55 wt % silver loading, the volume resistivity of ICAs decreased to 4.5 ×10-3 from 5.2×10-2 cured at 250 0C and 180 0C, respectively. However, there is almost no effect on the high silver loading. The in situ monitoring the variations in electrical resistance of the ICAs with 65 wt % silver loading was studied during the curing process, and it was found that the resistance reached to 1.99 ×106 Ω at 180 0C after cured for 27 min, and reached to 1.39 ×10-3 Ω for 40 min, and 18.8 Ω for 60 min and the cooling process has almost no effect on the electrical resistance of the ICAs. The reasons for the dependence of the bulk resistivity on temperatures were also discussed in terms of the dispersing of the silver flakes in ICAs by SEM.
In this paper, a typical isotropic conductive adhesives (ICAs) composed of an epoxy-based binder containing micro-sized silver flakes was prepared and the effects of the different curing procedures on the electrical properties of the ICAs were investigated. The results showed that there is greater influence of the curing temperature on 55 wt % silver loading, the volume resistivity of ICAs decreased to 4.5 ×10-3 from 5.2×10-2 cured at 250 0C and 180 0C, respectively. However, there is almost no effect on the high silver loading. The in situ monitoring the variations in electrical resistance of the ICAs with 65 wt % silver loading was studied during the curing process, and it was found that the resistance reached to 1.99 ×106 Ω at 180 0C after cured for 27 min, and reached to 1.39 ×10-3 Ω for 40 min, and 18.8 Ω for 60 min and the cooling process has almost no effect on the electrical resistance of the ICAs. The reasons for the dependence of the bulk resistivity on temperatures were also discussed in terms of the dispersing of the silver flakes in ICAs by SEM.
2016, 45(10):2529-2533.
Abstract:
The hot compression test was conducted by a Gleeble3500 dynamic hot-simulation testing machine to study the hot deformation behavior of 3003/4004 two-layered aluminum alloy. The test was conducted at various temperatures (300, 350, 400, and 450 ℃) with various strain rate of 0.05s-1, 0.5s-1, 5s-1, 25s-1. The compression curve shows a sharp increases for the effect of work-hardening, then it goes smooth for dynamic recovery and recrystallization happened. According to the experimental results, the peak stress was decreased as the strain rate reduced and the temperature increased. Finally a constitution equation describes the relationship of strain rate() ,deformation temperature (T) and flow stress (σ) was achieved.
The hot compression test was conducted by a Gleeble3500 dynamic hot-simulation testing machine to study the hot deformation behavior of 3003/4004 two-layered aluminum alloy. The test was conducted at various temperatures (300, 350, 400, and 450 ℃) with various strain rate of 0.05s-1, 0.5s-1, 5s-1, 25s-1. The compression curve shows a sharp increases for the effect of work-hardening, then it goes smooth for dynamic recovery and recrystallization happened. According to the experimental results, the peak stress was decreased as the strain rate reduced and the temperature increased. Finally a constitution equation describes the relationship of strain rate() ,deformation temperature (T) and flow stress (σ) was achieved.
2016, 45(10):2534-2538.
Abstract:
In this paper, the YBa2Cu3O7-x (YBCO) films were prepared on LaAlO3 (100) substrate using a low-fluorine sol-gel method. The effect of the oxygen content during firing YBCO films at 725 °C on the critical current density (Jc) of the resulting YBCO films were investigated. It is found that all the YBCO films fired in the oxygen content scale of 100~1700 ppm exhibit good biaxial-texture characteristics. However, the YBCO film is less dense when the oxygen content is low and thus the critical current density (Jc) of the film is inferior. The film surface becomes denser with increasing the oxygen content during the firing process, and Jc of the film reaches 4.3 MA/cm2 when the oxygen content is elevated to 300 ppm. Furthermore, many copper-rich second phases appear on the films surfaces and become more gradually with the further elevating the oxygen content, resulting in the decline of Jc.
In this paper, the YBa2Cu3O7-x (YBCO) films were prepared on LaAlO3 (100) substrate using a low-fluorine sol-gel method. The effect of the oxygen content during firing YBCO films at 725 °C on the critical current density (Jc) of the resulting YBCO films were investigated. It is found that all the YBCO films fired in the oxygen content scale of 100~1700 ppm exhibit good biaxial-texture characteristics. However, the YBCO film is less dense when the oxygen content is low and thus the critical current density (Jc) of the film is inferior. The film surface becomes denser with increasing the oxygen content during the firing process, and Jc of the film reaches 4.3 MA/cm2 when the oxygen content is elevated to 300 ppm. Furthermore, many copper-rich second phases appear on the films surfaces and become more gradually with the further elevating the oxygen content, resulting in the decline of Jc.
2016, 45(10):2539-2542.
Abstract:
With the consideration of Orowan strengthening effect, a new constitutive model of particulate-reinforced magnesium matrix nanocomposites for thixotropic plastic forming was derived by analyzing relationships among parameters (stress , strain , strain rate , liquid phase rate fL, volume fraction of nano-reinforcement fp, temperature T). The multiple nonlinear regression method was used to determine the parameters in the constitutive model. The findings indicate that there exists a specific constitutive relationship of thixotropic plastic forming of nanocomposites and the corresponding model was proposed. The calculated values obtained from the constitutive model had good agreement with the experimental results. As a result, the constitutive model provides references for the thixotropic forming theory, simulation and fabrication of nanocomposites.
With the consideration of Orowan strengthening effect, a new constitutive model of particulate-reinforced magnesium matrix nanocomposites for thixotropic plastic forming was derived by analyzing relationships among parameters (stress , strain , strain rate , liquid phase rate fL, volume fraction of nano-reinforcement fp, temperature T). The multiple nonlinear regression method was used to determine the parameters in the constitutive model. The findings indicate that there exists a specific constitutive relationship of thixotropic plastic forming of nanocomposites and the corresponding model was proposed. The calculated values obtained from the constitutive model had good agreement with the experimental results. As a result, the constitutive model provides references for the thixotropic forming theory, simulation and fabrication of nanocomposites.
2016, 45(10):2543-2548.
Abstract:
A SiC/MoSi2 alternating multilayer coating was produced on Carbon/Carbon (C/C) surface to protect it against oxidation by a magnetron sputtering method . The microstructural characteristic, oxidation behavior and oxidation mechanism of the SiC/MoSi2 multilayer coating were investigated. The as-received coating exhibited dense columnar structure and outstanding uniformity in thickness. The coated C/C composites performed a superior oxidation resistance, and its weight loss was only 3.2x10-2g/cm2 after oxidation at 1500℃ for 60min. The weight loss of the coated C/C composites was considered to be related with the penetration crack generated during the oxidation of the coating.
A SiC/MoSi2 alternating multilayer coating was produced on Carbon/Carbon (C/C) surface to protect it against oxidation by a magnetron sputtering method . The microstructural characteristic, oxidation behavior and oxidation mechanism of the SiC/MoSi2 multilayer coating were investigated. The as-received coating exhibited dense columnar structure and outstanding uniformity in thickness. The coated C/C composites performed a superior oxidation resistance, and its weight loss was only 3.2x10-2g/cm2 after oxidation at 1500℃ for 60min. The weight loss of the coated C/C composites was considered to be related with the penetration crack generated during the oxidation of the coating.
2016, 45(10):2549-2554.
Abstract:
High temperature deformation behavior of BFe10-1-2 cupronickel alloy under compression in the temperature range of 1023~1273K and strain rate range of 0.001~10s-1 were investigated for the sake of acquiring the optimum hot deformation processing parameters. The high temperature deformation behavior of BFe10-1-2 cupronickel alloy was characterized based on the analysis of the flow stress, kinetics and processing map. The activation energy for deformation obtained during high temperature compression of BFe10-1-2 cupronickel alloy was 425.299KJ/mol. A constitutive equation was then developed to describe the flow stress as a function of Zener-Holloman parameter and true strain. By comparing the calculated flow stress and the measured flow stress, the validity of the constitutive equation was verified. The results showed that the flow stress values obtained from the constitutive equation could track the experimental results. Thereafter, the processing map based on dynamic materials model was established, and the validation of processing map was investigated from the macro appearance and microstructure of compressed BFe10-1-2 cupronickel alloy.
High temperature deformation behavior of BFe10-1-2 cupronickel alloy under compression in the temperature range of 1023~1273K and strain rate range of 0.001~10s-1 were investigated for the sake of acquiring the optimum hot deformation processing parameters. The high temperature deformation behavior of BFe10-1-2 cupronickel alloy was characterized based on the analysis of the flow stress, kinetics and processing map. The activation energy for deformation obtained during high temperature compression of BFe10-1-2 cupronickel alloy was 425.299KJ/mol. A constitutive equation was then developed to describe the flow stress as a function of Zener-Holloman parameter and true strain. By comparing the calculated flow stress and the measured flow stress, the validity of the constitutive equation was verified. The results showed that the flow stress values obtained from the constitutive equation could track the experimental results. Thereafter, the processing map based on dynamic materials model was established, and the validation of processing map was investigated from the macro appearance and microstructure of compressed BFe10-1-2 cupronickel alloy.
2016, 45(10):2555-2560.
Abstract:
The formula to calculate the impact factor of binding interface (λ) was proposed and derived based on the composite of steel body and Babbitt layer. ZChSnSb11-6/20 steel composites with or without tin layer were prepared by arc spraying technology. And the mechanical properties were investigated. Then the mathematical relationship between the impact factor of binding interface (λ) and proportion of Babbitt (ξ) was obtained. Results revealed that the impact factor of binding interface of composites without tinning (λ1) decreased monotonically with the proportion of Babbitt (ξ). However, for the composites with tinning, the function of λ2 and ξ exits an inflection point which is ξ=0.597. This inflection point suggested that there was an optimal thickness of Babbitt layer, and the best binding between 20 steel and Babbitt layer was obtained. It was validated that the process of tin layer enhanced the interfacial binding properties of composites, and the binding force of interface was maximum when ξ was 0.6.
The formula to calculate the impact factor of binding interface (λ) was proposed and derived based on the composite of steel body and Babbitt layer. ZChSnSb11-6/20 steel composites with or without tin layer were prepared by arc spraying technology. And the mechanical properties were investigated. Then the mathematical relationship between the impact factor of binding interface (λ) and proportion of Babbitt (ξ) was obtained. Results revealed that the impact factor of binding interface of composites without tinning (λ1) decreased monotonically with the proportion of Babbitt (ξ). However, for the composites with tinning, the function of λ2 and ξ exits an inflection point which is ξ=0.597. This inflection point suggested that there was an optimal thickness of Babbitt layer, and the best binding between 20 steel and Babbitt layer was obtained. It was validated that the process of tin layer enhanced the interfacial binding properties of composites, and the binding force of interface was maximum when ξ was 0.6.
2016, 45(10):2561-2567.
Abstract:
The multi-paths compression with sequential RD>ND>RD>ND(RD-Rolling Direction；ND-Normal Direction) was performed on the AZ31 magnesium alloy rolled sheet, and mechanical property of the previous deformation were studied, the electron backscatter diffraction (EBSD) technique was applied to track the grain orientation evolution during the above deformation, and activations of twin variants were analyzed. The results show that the deformation mechanism of {10-12} tensile twin ->{10-12} untwin ->{10-12} tensile twin and {10-12} untwin are sequentially related to each compression during the above deformation. The yielding strength was significantly decreased during the first untwining, but the yielding strengths were increased for both twinning and untwining during the following deformations, and there are not obvious differences between them. The activation of untwinning follows the Schmid criterion, and there is an obvious selective tendency for twin variant activation, twin variant t3 or t4 were activated to start the untwinning.
The multi-paths compression with sequential RD>ND>RD>ND(RD-Rolling Direction；ND-Normal Direction) was performed on the AZ31 magnesium alloy rolled sheet, and mechanical property of the previous deformation were studied, the electron backscatter diffraction (EBSD) technique was applied to track the grain orientation evolution during the above deformation, and activations of twin variants were analyzed. The results show that the deformation mechanism of {10-12} tensile twin ->{10-12} untwin ->{10-12} tensile twin and {10-12} untwin are sequentially related to each compression during the above deformation. The yielding strength was significantly decreased during the first untwining, but the yielding strengths were increased for both twinning and untwining during the following deformations, and there are not obvious differences between them. The activation of untwinning follows the Schmid criterion, and there is an obvious selective tendency for twin variant activation, twin variant t3 or t4 were activated to start the untwinning.
2016, 45(10):2568-2572.
Abstract:
The erosion-corrosion behavior of directional solidification Fe-3.5B alloy in flowing liquid zinc was investigated by rotating disk technique. Microstructural morphology of erosion-corrosion interface was observed by SEM, the effects of orientation and space of Fe2B on the erosion-corrosion in the flowing liquid zinc were analyzed. The results show that the erosion rate quickly decreases with the extension of erosion time when the Fe2B is parallel to the flowing direction of liquid zinc (labeled Fe2B∥ sample) and the erosion rate slowly decreases with the extension of corrosion time when the Fe2B is perpendicular to the flowing direction of liquid zinc (labeled Fe2B⊥ sample). The erosion rate of directional solidification Fe-3.5B alloy (Fe2B∥ sample) increases first and then decreases with the increase of Fe2B space. When the space of Fe2B is 3.67μm, the corrosion rate of transverse sample possesses the minimum value of erosion-corrosion rate. The corrosion rate of longitudinal sample reaches the minimum value of erosion-corrosion rate when the space of Fe2B is 1.87μm. The microstructure of erosion-corrosion interface is dependent on the Fe2B space, and the appropriate Fe2B space is beneficial to form a good erosion compound layer which shows an “interface pinning effect” and inhibits erosion-corrosion.
The erosion-corrosion behavior of directional solidification Fe-3.5B alloy in flowing liquid zinc was investigated by rotating disk technique. Microstructural morphology of erosion-corrosion interface was observed by SEM, the effects of orientation and space of Fe2B on the erosion-corrosion in the flowing liquid zinc were analyzed. The results show that the erosion rate quickly decreases with the extension of erosion time when the Fe2B is parallel to the flowing direction of liquid zinc (labeled Fe2B∥ sample) and the erosion rate slowly decreases with the extension of corrosion time when the Fe2B is perpendicular to the flowing direction of liquid zinc (labeled Fe2B⊥ sample). The erosion rate of directional solidification Fe-3.5B alloy (Fe2B∥ sample) increases first and then decreases with the increase of Fe2B space. When the space of Fe2B is 3.67μm, the corrosion rate of transverse sample possesses the minimum value of erosion-corrosion rate. The corrosion rate of longitudinal sample reaches the minimum value of erosion-corrosion rate when the space of Fe2B is 1.87μm. The microstructure of erosion-corrosion interface is dependent on the Fe2B space, and the appropriate Fe2B space is beneficial to form a good erosion compound layer which shows an “interface pinning effect” and inhibits erosion-corrosion.
2016, 45(10):2573-2577.
Abstract:
W–1% La2O3 alloy is considered as one of the candidate material for plasma-facing components of future fusion reactors. The phases of as-forged W–1% La2O3 alloy, especially the nano-sized particle phases, have been investigated using transmission electron microscopes．Eight kinds of particle phases have been found in the alloy. They are: three kinds of La2O3 phases; two kinds of WO3 phases; W3O8 phase; La0.14WO3 phase and (La2O3)5WO3 phase. La2O3, WO3 and W3O8 are dominant nano-sized phases in the alloy. These particles have sizes ranging from about 20 nm to about 100 nm. The possible formation processes of these particle phases are also discussed.
W–1% La2O3 alloy is considered as one of the candidate material for plasma-facing components of future fusion reactors. The phases of as-forged W–1% La2O3 alloy, especially the nano-sized particle phases, have been investigated using transmission electron microscopes．Eight kinds of particle phases have been found in the alloy. They are: three kinds of La2O3 phases; two kinds of WO3 phases; W3O8 phase; La0.14WO3 phase and (La2O3)5WO3 phase. La2O3, WO3 and W3O8 are dominant nano-sized phases in the alloy. These particles have sizes ranging from about 20 nm to about 100 nm. The possible formation processes of these particle phases are also discussed.
2016, 45(10):2578-2582.
Abstract:
The expanding curves of BT25 titanium alloy under different cooling rates was investigated using dilatometry method. It was proved that the expansion method was able to measure accurately phase transformation of BT25 titanium alloy at different cooling rates. The continuous cooling transformation ( CCT ) diagram of this alloy was obtained by means of X ray diffractometry ( XRD), scanning electron microscopy(SEM) and micro-hardness。As well as the effect of cooling rate on microstructure evolution was investigated .The results showed that the Widmanstaten structure is obtained at the cooling rate of less than C1 (1~3 ℃?s -1); therefore, α" phase is generated at the cooling rate of greater than C2 (50 ~100 ℃?s -1) ; The microstructure consists of Widmanstaten structure and α" at the cooling rate from C1 to C2. With the cooling rate decreases, the quantity of Widmanstaten structure increases and the quantity of α" phase decreases in this microstructure. The micro-hardness of BT25 alloy decreases as the cooling rates decreasing.
The expanding curves of BT25 titanium alloy under different cooling rates was investigated using dilatometry method. It was proved that the expansion method was able to measure accurately phase transformation of BT25 titanium alloy at different cooling rates. The continuous cooling transformation ( CCT ) diagram of this alloy was obtained by means of X ray diffractometry ( XRD), scanning electron microscopy(SEM) and micro-hardness。As well as the effect of cooling rate on microstructure evolution was investigated .The results showed that the Widmanstaten structure is obtained at the cooling rate of less than C1 (1~3 ℃?s -1); therefore, α" phase is generated at the cooling rate of greater than C2 (50 ~100 ℃?s -1) ; The microstructure consists of Widmanstaten structure and α" at the cooling rate from C1 to C2. With the cooling rate decreases, the quantity of Widmanstaten structure increases and the quantity of α" phase decreases in this microstructure. The micro-hardness of BT25 alloy decreases as the cooling rates decreasing.
2016, 45(10):2583-2586.
Abstract:
Mo-doped Alumina (Al2O3/Mo) ceramic composites were prepared by powder metallurgical process. The influence of Mo doping amount on the microstructure and electrical properties of the composites were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and other testing analysis methods. The results show that the composites were composed of Al2O3 and Mo phases and without any impurities. When the amount of Mo is below 20wt.%, there are no obvious changes in resistivity (>1012Ω?cm) and permisitvity(8-9) for the composites, but the refaining of grain. When doping amount over 20wt.%, the Mo transforme from dispersed phase into the continuous phase while volume resistivity decrease to 1010Ω ? cm shaply; When doping amount is 40wt.%, since the throughout matrix of Mo is formed, the volume resistivity decrease slow, steady at about 10Ω ? cm. Therefore, by adjusting the amount and phase distribution of Mo in Al2O3 matix, ceramic/metal composite materials with different resistivity can be prepeared.
Mo-doped Alumina (Al2O3/Mo) ceramic composites were prepared by powder metallurgical process. The influence of Mo doping amount on the microstructure and electrical properties of the composites were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and other testing analysis methods. The results show that the composites were composed of Al2O3 and Mo phases and without any impurities. When the amount of Mo is below 20wt.%, there are no obvious changes in resistivity (>1012Ω?cm) and permisitvity(8-9) for the composites, but the refaining of grain. When doping amount over 20wt.%, the Mo transforme from dispersed phase into the continuous phase while volume resistivity decrease to 1010Ω ? cm shaply; When doping amount is 40wt.%, since the throughout matrix of Mo is formed, the volume resistivity decrease slow, steady at about 10Ω ? cm. Therefore, by adjusting the amount and phase distribution of Mo in Al2O3 matix, ceramic/metal composite materials with different resistivity can be prepeared.
2016, 45(10):2587-2592.
Abstract:
The ceramic oxide film on the surface of 7475 aluminum alloy was prepared by micro arc oxidation. The surface and interface morphology, chemical composition and phase were analyzed via SEM, EDS, XRD and etc. Energy spectrum analysis was conducted to analyze the distribution of chemical composition on the surface and interface. Adhesion strength of ceramic oxide film interface was measured by scratch. The results show that a layer of rough porous ceramic oxide film, whose chemical element is distributed correspondingly with its phase, is formed on the surface of 7475 aluminum alloy by micro arc oxidation. The Al2O3 mainly composed of α-Al2O3 and γ-Al2O3 is formed on the Al base by combining with diffusing O atoms, while the enrichment of Si atoms forms Si-Al-O phase. The ceramic oxide film is composed by gap layer, dense layer and film-substrate layer with thickness of about 50 μm.
The ceramic oxide film on the surface of 7475 aluminum alloy was prepared by micro arc oxidation. The surface and interface morphology, chemical composition and phase were analyzed via SEM, EDS, XRD and etc. Energy spectrum analysis was conducted to analyze the distribution of chemical composition on the surface and interface. Adhesion strength of ceramic oxide film interface was measured by scratch. The results show that a layer of rough porous ceramic oxide film, whose chemical element is distributed correspondingly with its phase, is formed on the surface of 7475 aluminum alloy by micro arc oxidation. The Al2O3 mainly composed of α-Al2O3 and γ-Al2O3 is formed on the Al base by combining with diffusing O atoms, while the enrichment of Si atoms forms Si-Al-O phase. The ceramic oxide film is composed by gap layer, dense layer and film-substrate layer with thickness of about 50 μm.
2016, 45(10):2593-2597.
Abstract:
Abstract: Four groups of different carbon and CeO2 content of ultrafine WC-9Ni-0.4Cr3C2 cemented carbide samples were prepared by powder metallurgy method. The thermal properties of the alloys were measured and analyzed using thermal constant Hot Disk analyzer through transient plane heat source method (TPS) technology; meanwhile, the phase composition and different surface morphology of the alloys after sintering were also studied by XRD, SEM and EDX analysis. The results show that, with the CeO2 content increase, the thermal conductivity and thermal diffusion coefficient of the alloy decrease, while the heat capacity increases in smaller extent. When carbon content in the WC-9Ni-0.4Cr3C2-CeO2 is low, Ce tends to gather in the alloys’ surface in the form of sulfide and oxide. With the increasing of carbon content, the gathered phenomenon of Ce in the alloy’s surface is gradually disappearing, and the thermal conductivity and thermal diffusion coefficient rise obviously. However, the specific heat capacity changes a little.
Abstract: Four groups of different carbon and CeO2 content of ultrafine WC-9Ni-0.4Cr3C2 cemented carbide samples were prepared by powder metallurgy method. The thermal properties of the alloys were measured and analyzed using thermal constant Hot Disk analyzer through transient plane heat source method (TPS) technology; meanwhile, the phase composition and different surface morphology of the alloys after sintering were also studied by XRD, SEM and EDX analysis. The results show that, with the CeO2 content increase, the thermal conductivity and thermal diffusion coefficient of the alloy decrease, while the heat capacity increases in smaller extent. When carbon content in the WC-9Ni-0.4Cr3C2-CeO2 is low, Ce tends to gather in the alloys’ surface in the form of sulfide and oxide. With the increasing of carbon content, the gathered phenomenon of Ce in the alloy’s surface is gradually disappearing, and the thermal conductivity and thermal diffusion coefficient rise obviously. However, the specific heat capacity changes a little.
2016, 45(10):2598-2604.
Abstract:
In order to analyze the effect of thermal behavior on microstructural evolution of laser deposition manufacturing process, a finite element model was constructed to simulate the temperature field distribution and thermal cycle characteristics. The simulation results showed that any node in substrate and deposition layer experienced heating or cooling cyclically. And the macro and microstructure of laser deposition manufacturing specimen were investigated to determine the evolution of microstructural features in multi-pass deposition layers. The macro and microstructures exhibited epitaxial coarse columnar prior β grains with basketweave or colony α lamella. The width of α lamella changed gradiently, and α lamella had basketweave Widmanstatten or colonies Widmanstatten morphology. The line scanning results by energy dispersive spectrometer (EDS) showed that major alloy elements, Ti, Al, Zr, Mo and V, were distributed uniformly from the substrate to deposited layer without fluctuation and segregation, which showed that evolution of microstructure was not a result of segregation but heat history.
In order to analyze the effect of thermal behavior on microstructural evolution of laser deposition manufacturing process, a finite element model was constructed to simulate the temperature field distribution and thermal cycle characteristics. The simulation results showed that any node in substrate and deposition layer experienced heating or cooling cyclically. And the macro and microstructure of laser deposition manufacturing specimen were investigated to determine the evolution of microstructural features in multi-pass deposition layers. The macro and microstructures exhibited epitaxial coarse columnar prior β grains with basketweave or colony α lamella. The width of α lamella changed gradiently, and α lamella had basketweave Widmanstatten or colonies Widmanstatten morphology. The line scanning results by energy dispersive spectrometer (EDS) showed that major alloy elements, Ti, Al, Zr, Mo and V, were distributed uniformly from the substrate to deposited layer without fluctuation and segregation, which showed that evolution of microstructure was not a result of segregation but heat history.
2016, 45(10):2605-2608.
Abstract:
The Ni-W-Er2O3 coating on 45# steel substrate was fabricated by electrodeposition. The microstructure and morphology of the composite coatings were analyzed by SEM, EDS and XRD, etc. At the same time, the thickness, microhardness and corrosion resistance of the coatings were measured by means of the magnetic thickness apparatus, microhardness tester and electrochemical workstation. The results show that the composite coating with a compact structure is not found to have obvious flaws and has a good adhesion with the matrix. The composite coating can obtain a high hardness, high tungsten content and better corrosion resistance with the addition of rare earth oxide Er2O3. When the addition amount is 16 g/L, the comprehensive performance of the coating is best.
The Ni-W-Er2O3 coating on 45# steel substrate was fabricated by electrodeposition. The microstructure and morphology of the composite coatings were analyzed by SEM, EDS and XRD, etc. At the same time, the thickness, microhardness and corrosion resistance of the coatings were measured by means of the magnetic thickness apparatus, microhardness tester and electrochemical workstation. The results show that the composite coating with a compact structure is not found to have obvious flaws and has a good adhesion with the matrix. The composite coating can obtain a high hardness, high tungsten content and better corrosion resistance with the addition of rare earth oxide Er2O3. When the addition amount is 16 g/L, the comprehensive performance of the coating is best.
2016, 45(10):2609-2614.
Abstract:
Extruded microstructures of Mg-6Zn-xGd (x=0~4) alloys were investigated by optical microscopy (OM) and scanning electron microscopy (SEM). Meanwhile, the tensile mechanical property and corrosion property were tested. The results show that extruded microstructure is refined obviously increasing the Gd content, where the average grain size decreases from 12 ?m for Mg-6Zn alloy to 2 ?m for Mg-6Zn-3.41Gd alloy. Extruded tensile mechanical property is enhanced obviously. Tensile strength σb and yield strength σ0.2 increase gradually from 295 MPa and 193 MPa for Mg-6Zn alloy to 350 MPa and 325 MPa for Mg-6Zn-3.41Gd alloy. Elongation δ first decreases, and then increases, which is not lower than 10%. Extruded Mg-6Zn alloy exhibits the slow corrosion rate with typical local corrosion. When a little Gd content (0.66%) is added, the corrosion rate increases slightly, however its corrosion becomes more uniform and changes to the uniform corrosion. When more Gd content (1.66% and 3.41%) is added, the corrosion resistance deteriorates sharply.
Extruded microstructures of Mg-6Zn-xGd (x=0~4) alloys were investigated by optical microscopy (OM) and scanning electron microscopy (SEM). Meanwhile, the tensile mechanical property and corrosion property were tested. The results show that extruded microstructure is refined obviously increasing the Gd content, where the average grain size decreases from 12 ?m for Mg-6Zn alloy to 2 ?m for Mg-6Zn-3.41Gd alloy. Extruded tensile mechanical property is enhanced obviously. Tensile strength σb and yield strength σ0.2 increase gradually from 295 MPa and 193 MPa for Mg-6Zn alloy to 350 MPa and 325 MPa for Mg-6Zn-3.41Gd alloy. Elongation δ first decreases, and then increases, which is not lower than 10%. Extruded Mg-6Zn alloy exhibits the slow corrosion rate with typical local corrosion. When a little Gd content (0.66%) is added, the corrosion rate increases slightly, however its corrosion becomes more uniform and changes to the uniform corrosion. When more Gd content (1.66% and 3.41%) is added, the corrosion resistance deteriorates sharply.
2016, 45(10):2615-2620.
Abstract:
In this paper, the hot compression tests were carried out, the true stress-strain curves were obtained during AZ31B cast rod deformation, and the effects of deformation temperatures and strain rates on flow stress were analyzed. It was found that the peak strain increased with the increasing strain rate and decreasing deformation temperature, and it is advantageous for dynamic recovery and recrystallization to reduce strain rate and properly raise deformation temperature. Moreover, the flow stress prediction model, which was established by means of multiple regression analysis can illustrate the strain-sensitivity of flow stress. Furthermore, it is investigated that the correlation?coefficient of predicted and experimental values is up to 0.9926, indicating that this model is more accurate in terms of predicting the flow stress of as-cast AZ31B magnesium?alloy and can better?describe its flow behavior during hot deformation.
In this paper, the hot compression tests were carried out, the true stress-strain curves were obtained during AZ31B cast rod deformation, and the effects of deformation temperatures and strain rates on flow stress were analyzed. It was found that the peak strain increased with the increasing strain rate and decreasing deformation temperature, and it is advantageous for dynamic recovery and recrystallization to reduce strain rate and properly raise deformation temperature. Moreover, the flow stress prediction model, which was established by means of multiple regression analysis can illustrate the strain-sensitivity of flow stress. Furthermore, it is investigated that the correlation?coefficient of predicted and experimental values is up to 0.9926, indicating that this model is more accurate in terms of predicting the flow stress of as-cast AZ31B magnesium?alloy and can better?describe its flow behavior during hot deformation.
28 Effect of adding microscale Er and Zr elements on the Microstructure and Properties of ZL205A Alloy
2016, 45(10):2621-2627.
Abstract:
Rare earth (RE) elements have important effect on the microstructure and properties of cast aluminum alloys. With addition of 0.05, 0.15 and 0.25 wt% Er and Zr elements to the ZL205A alloy respectively, this article investigated the effect of different content of RE elements on the microstructure and properties of as-cast and T5 heat-treated alloys. The results show that adding micro scale Er and Zr elements can effectively improve the fluidity of liquid alloy, refine the grains and promote the theta phase to concentrate on the intersection of the grain boundaries. When the addition amount is 0.05 wt%, the mechanical properties of as-cast alloy reduced greatly while compared with the initial alloy; after T5 heat-treatment, the tensile strength, Vickers hardness and elongation can respectively reach 358 MPa, 107 and 2%, and the comprehensive performance is the best. T5 heat-treatment can make the microstructure and composition uniform, and also lead solute atoms to diffuse sufficiently, thus hindering the dislocation movement and sub-boundary migration during deformation process, finally taking adverse impact on the elongation.
Rare earth (RE) elements have important effect on the microstructure and properties of cast aluminum alloys. With addition of 0.05, 0.15 and 0.25 wt% Er and Zr elements to the ZL205A alloy respectively, this article investigated the effect of different content of RE elements on the microstructure and properties of as-cast and T5 heat-treated alloys. The results show that adding micro scale Er and Zr elements can effectively improve the fluidity of liquid alloy, refine the grains and promote the theta phase to concentrate on the intersection of the grain boundaries. When the addition amount is 0.05 wt%, the mechanical properties of as-cast alloy reduced greatly while compared with the initial alloy; after T5 heat-treatment, the tensile strength, Vickers hardness and elongation can respectively reach 358 MPa, 107 and 2%, and the comprehensive performance is the best. T5 heat-treatment can make the microstructure and composition uniform, and also lead solute atoms to diffuse sufficiently, thus hindering the dislocation movement and sub-boundary migration during deformation process, finally taking adverse impact on the elongation.
29 Corrosion Processing Dissolution Characteristics of Ti-6Al-4V in Hydrofluoric –Nitric Acid System
2016, 45(10):2628-2634.
Abstract:
The effects of main solution ingredients, temperature on dissolution and characteristics of corrosion processing for Ti-6Al-4V in hydrofluoric-nitric acid system were investigated by means of E-t curve, potentiodynamic polarization curve. Moreover anodic and cathodic reaction rate measurements were used to discuss corrosion dynamics. The process of “attack→oxidation→dissolution” repeats continuously during the course of corrosion dissolution of titanium alloy in this solution system. The growth and destruction of passive film simultaneously occur. Corrosion processing rate tends to be stable when the growth of passive film and dissolution of the substrate achieve dynamic balance. At the early stage of corrosion processing, corrosion potential changes to a more positive value when the concentration of hydrofluoric acid is low, indicating that oxide film is difficult to be attacked, while in case of higher concentration, corrosion potential becomes negative quickly as oxide film is easily dissolved. Corrosion dissolution rate is affected by hydrofluoric acid concentration and temperature. With the increase of hydrofluoric acid concentration and temperature, the activation energy declines, corrosion dissolution is enhanced. Temperature plays a leading role under the condition of lower concentration of hydrofluoric acid. When the concentration reaches 80mL/L, the influence of temperature attenuates and the concentration of hydrofluoric acid becomes the major factor.
The effects of main solution ingredients, temperature on dissolution and characteristics of corrosion processing for Ti-6Al-4V in hydrofluoric-nitric acid system were investigated by means of E-t curve, potentiodynamic polarization curve. Moreover anodic and cathodic reaction rate measurements were used to discuss corrosion dynamics. The process of “attack→oxidation→dissolution” repeats continuously during the course of corrosion dissolution of titanium alloy in this solution system. The growth and destruction of passive film simultaneously occur. Corrosion processing rate tends to be stable when the growth of passive film and dissolution of the substrate achieve dynamic balance. At the early stage of corrosion processing, corrosion potential changes to a more positive value when the concentration of hydrofluoric acid is low, indicating that oxide film is difficult to be attacked, while in case of higher concentration, corrosion potential becomes negative quickly as oxide film is easily dissolved. Corrosion dissolution rate is affected by hydrofluoric acid concentration and temperature. With the increase of hydrofluoric acid concentration and temperature, the activation energy declines, corrosion dissolution is enhanced. Temperature plays a leading role under the condition of lower concentration of hydrofluoric acid. When the concentration reaches 80mL/L, the influence of temperature attenuates and the concentration of hydrofluoric acid becomes the major factor.
2016, 45(10):2635-2641.
Abstract:
The structure, phase composition and element distribution of the oxidation scales were analyzed by XPS for the Ti-42Al-8Nb alloys which was oxided at 900 oC for 20 h in air. It is noted that the outside of oxidation scale was composed of TiO2 only achieved by XPS, which was different from the results of the XRD analysis. The mixture of Al2O3, three titanium oxides and a few nitrides exist near the outside of the scale. The contents of Ti oxide with high valence state increased along the direction from the substrate to the outside of the sample. There was no presence of the other two Ti oxides with lower valence state in the outside of the scale, only TiO2 existed. It is concluded that the whole process of the TiAl alloy was promoted by the dissolution, diffusion of the O atom, which resulted in the multi-stage variation in the scale with different depth for different oxidation time, meanwhile resulted in the differences of the structure, composition and contents in the oxidation scales.
The structure, phase composition and element distribution of the oxidation scales were analyzed by XPS for the Ti-42Al-8Nb alloys which was oxided at 900 oC for 20 h in air. It is noted that the outside of oxidation scale was composed of TiO2 only achieved by XPS, which was different from the results of the XRD analysis. The mixture of Al2O3, three titanium oxides and a few nitrides exist near the outside of the scale. The contents of Ti oxide with high valence state increased along the direction from the substrate to the outside of the sample. There was no presence of the other two Ti oxides with lower valence state in the outside of the scale, only TiO2 existed. It is concluded that the whole process of the TiAl alloy was promoted by the dissolution, diffusion of the O atom, which resulted in the multi-stage variation in the scale with different depth for different oxidation time, meanwhile resulted in the differences of the structure, composition and contents in the oxidation scales.
2016, 45(10):2642-2646.
Abstract:
The ultrasonic shot peening (USSP) was used to treat TC4 surface, the samples were loaded by four-point-bending fatigue test, and residual stress distribution before and after fatigue loading was tested by X-ray stress tester. By TEM equipment, microstructure of TC4 before and after fatigue loading was characterized. The results showed that the maximum residual compressive stress of surface nanocrystallization TC4 exceeded its yield strength; When the loads were higher than fatigue limit, the residual stress released and the residual stress field decreased significantly; When the loads were close to or lower than the fatigue limit, the residual stress field tended to be stable and was no longer evidently altered with the change of cyclic time and loads; The configuration and quantity of dislocations and dislocation cells were changed in the process of fatigue, the decrease of the dislocation density resulted in the relaxation of residual compressive stress.
The ultrasonic shot peening (USSP) was used to treat TC4 surface, the samples were loaded by four-point-bending fatigue test, and residual stress distribution before and after fatigue loading was tested by X-ray stress tester. By TEM equipment, microstructure of TC4 before and after fatigue loading was characterized. The results showed that the maximum residual compressive stress of surface nanocrystallization TC4 exceeded its yield strength; When the loads were higher than fatigue limit, the residual stress released and the residual stress field decreased significantly; When the loads were close to or lower than the fatigue limit, the residual stress field tended to be stable and was no longer evidently altered with the change of cyclic time and loads; The configuration and quantity of dislocations and dislocation cells were changed in the process of fatigue, the decrease of the dislocation density resulted in the relaxation of residual compressive stress.
2016, 45(10):2647-2652.
Abstract:
The film of LaMg2Ni9 Hydrogen Storage alloy is prepared in aqueous solution. The electrochemical performance were studied by cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS) and Tafel polarization curve. Sanning electronic microscope(SEM), X-ray diffractometer(XRD) and energy distribution spectrum(EDS)were used to research the phase structure, component and composition. The results showed that the LaMg2Ni9 film has a crudity surface with a cracke. The alloy film obtained at 40A/dm2, the△G≠reaches to 47.26kJ/mol, the Hydrogen evolution current density jo is 5.37 A/cm2, indicating it has higher hydrogen evolution activity; the electrode adsorption degree Q is 0.091F/cm2, indicating the film has better hydrogen storage function.
The film of LaMg2Ni9 Hydrogen Storage alloy is prepared in aqueous solution. The electrochemical performance were studied by cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS) and Tafel polarization curve. Sanning electronic microscope(SEM), X-ray diffractometer(XRD) and energy distribution spectrum(EDS)were used to research the phase structure, component and composition. The results showed that the LaMg2Ni9 film has a crudity surface with a cracke. The alloy film obtained at 40A/dm2, the△G≠reaches to 47.26kJ/mol, the Hydrogen evolution current density jo is 5.37 A/cm2, indicating it has higher hydrogen evolution activity; the electrode adsorption degree Q is 0.091F/cm2, indicating the film has better hydrogen storage function.
2016, 45(10):2653-2658.
Abstract:
Abstract: The different different zirconium content in Pb0.88La0.08(ZrxTi1-x)O3（x=0.30，055，0.80）(abbreviated as PLZT) thick films with 1μm thickness were successfully fabricated on LaNiO3/Si(100) by the sol-gel method. The effect of different zirconium content of the PLZT anti-ferroelectric thick films on the dielectric and energy-storage properties were studied scientifically. The results show that the structure of the PLZT anti-ferroelectric thick films was not affected, after zirconium content performance enhanced significantly, when ratio is (8/80/20), the energy-storage density (W) and energy-storage efficiency (η) were increased, and the maximum W=23.8J/cm3 and corresponding η=60% were obtained from the PLZT(8/80/20) thick films at 1400 kV/cm.
Abstract: The different different zirconium content in Pb0.88La0.08(ZrxTi1-x)O3（x=0.30，055，0.80）(abbreviated as PLZT) thick films with 1μm thickness were successfully fabricated on LaNiO3/Si(100) by the sol-gel method. The effect of different zirconium content of the PLZT anti-ferroelectric thick films on the dielectric and energy-storage properties were studied scientifically. The results show that the structure of the PLZT anti-ferroelectric thick films was not affected, after zirconium content performance enhanced significantly, when ratio is (8/80/20), the energy-storage density (W) and energy-storage efficiency (η) were increased, and the maximum W=23.8J/cm3 and corresponding η=60% were obtained from the PLZT(8/80/20) thick films at 1400 kV/cm.
2016, 45(10):2659-2663.
Abstract:
After superplastic tensile deformation and triple heat treatment, the effects of triple heat treatment on superplastic tensile microstructure of TC21 titanium alloy were investigated. The results show that dynamic recrystallization occurred obviously in the process of TC21 titanium alloy superplastic deformation. The α phase content became more decrease with increase of deformation temperature and α?β phase transition start to happen. After superplastic deformation and β solid solution heat treatment for the first time, TC21 titanium alloy obtain single-phase β organizations. Through a high temperature aging and a low temperature aging in the (α β) phase region, fine acicular α phase precipitates out on β matrix, and TC21 alloy obtain baskets organizations. Acicular α phase content increases with the increase of deformation temperature and the second heat treatment temperature. With the increase of deformation temperature and the second temperature, acicular α phase content increases, and α grain grew up and intertwined which basketweave microstructure significantly.
After superplastic tensile deformation and triple heat treatment, the effects of triple heat treatment on superplastic tensile microstructure of TC21 titanium alloy were investigated. The results show that dynamic recrystallization occurred obviously in the process of TC21 titanium alloy superplastic deformation. The α phase content became more decrease with increase of deformation temperature and α?β phase transition start to happen. After superplastic deformation and β solid solution heat treatment for the first time, TC21 titanium alloy obtain single-phase β organizations. Through a high temperature aging and a low temperature aging in the (α β) phase region, fine acicular α phase precipitates out on β matrix, and TC21 alloy obtain baskets organizations. Acicular α phase content increases with the increase of deformation temperature and the second heat treatment temperature. With the increase of deformation temperature and the second temperature, acicular α phase content increases, and α grain grew up and intertwined which basketweave microstructure significantly.
2016, 45(10):2664-2670.
Abstract:
The effects of short-time electromagnetic stirring(EMS),grain refiner and their combined effects on microstructure and radial homogeneity of large-volume semisolid slurry of 7A04 alloy were investigated.The results indicate that 7A04 alloy semisolid slurry with fine and globular primary α-Al grains could be achieved and the homogeneity of slurry could be improved by either short-time EMS or addition of grain refining element Zr,Sc. Optimum microstructure with average equivalent diameter of 36um，shape factor of 0.68, coefficient of variation Cv of 0.8% at 631℃ could be obtained by the combined action of short-time EMS and grain refiner.As the temperature decreased,microstructure of semisolid slurry of 7A04 alloy coarsened and homogeneity of microstructure of slurry deteriorated,while the shape factor had little change.
The effects of short-time electromagnetic stirring(EMS),grain refiner and their combined effects on microstructure and radial homogeneity of large-volume semisolid slurry of 7A04 alloy were investigated.The results indicate that 7A04 alloy semisolid slurry with fine and globular primary α-Al grains could be achieved and the homogeneity of slurry could be improved by either short-time EMS or addition of grain refining element Zr,Sc. Optimum microstructure with average equivalent diameter of 36um，shape factor of 0.68, coefficient of variation Cv of 0.8% at 631℃ could be obtained by the combined action of short-time EMS and grain refiner.As the temperature decreased,microstructure of semisolid slurry of 7A04 alloy coarsened and homogeneity of microstructure of slurry deteriorated,while the shape factor had little change.
2016, 45(10):2671-2676.
Abstract:
The NaMgF3 films were fabricated on the surface of Mg-Gd-Zn-Zr magnesium alloy by TUCM. Their corrosion properties were evaluated by dripping test, electrochemical test and hydrogen evaluation test, respectively. The microstructure and chemical composition of NaMgF3 films were analyzed by SEM and EDS, respectively. The results show that the NaMgF3 particles formed by TUCM are fine. The color change time of NaMgF3 film increases with increasing the process time. Their capacitive reactance arc radius and impedance value are obviously greater than that of magnesium alloy, while their corrosion current density and average hydrogen evolution rate are significantly smaller that of magnesium alloy in SBF. The NaMgF3 film promotes the deposition of Ca and P on the surface of magnesium alloy in the SBF. The new complex film of fluoride and phosphate formed by the corrosion of NaMgF3 film in the SBF will continue to protect the magnesium alloy from the corrosion
The NaMgF3 films were fabricated on the surface of Mg-Gd-Zn-Zr magnesium alloy by TUCM. Their corrosion properties were evaluated by dripping test, electrochemical test and hydrogen evaluation test, respectively. The microstructure and chemical composition of NaMgF3 films were analyzed by SEM and EDS, respectively. The results show that the NaMgF3 particles formed by TUCM are fine. The color change time of NaMgF3 film increases with increasing the process time. Their capacitive reactance arc radius and impedance value are obviously greater than that of magnesium alloy, while their corrosion current density and average hydrogen evolution rate are significantly smaller that of magnesium alloy in SBF. The NaMgF3 film promotes the deposition of Ca and P on the surface of magnesium alloy in the SBF. The new complex film of fluoride and phosphate formed by the corrosion of NaMgF3 film in the SBF will continue to protect the magnesium alloy from the corrosion
2016, 45(10):2677-2682.
Abstract:
As a new method, electropulsing treatment has a great impact on microstructure and properties of metallic meterials. In the present paper, the microstructure evolution of rolled ZK60 alloy was investigated by optical microscope (OM) and electron backscattered diffraction (EBSD). The properties were evaluated by tensile testing at room temperature. The complete recrystallization was liable to occur when the deformed ZK60 magnesium alloy sheets were treated by electropulsing in comparison with heat treatment. After electropusling treatment for 10min, the recrystallization grains with the average size of 3μm were obtained. The tensile stress of ZK60 alloy was improved to 310MPa and the tensile elongation was increased to 30.7%. However, the incomplete recrystallization occured in rolled ZK60 alloy which was treated by heat treatment with the same processing time. The electropulsing enhanced the nucleation rate of recrystallization for rolled ZK60 alloy and then accelerated the process of recrystallization.
As a new method, electropulsing treatment has a great impact on microstructure and properties of metallic meterials. In the present paper, the microstructure evolution of rolled ZK60 alloy was investigated by optical microscope (OM) and electron backscattered diffraction (EBSD). The properties were evaluated by tensile testing at room temperature. The complete recrystallization was liable to occur when the deformed ZK60 magnesium alloy sheets were treated by electropulsing in comparison with heat treatment. After electropusling treatment for 10min, the recrystallization grains with the average size of 3μm were obtained. The tensile stress of ZK60 alloy was improved to 310MPa and the tensile elongation was increased to 30.7%. However, the incomplete recrystallization occured in rolled ZK60 alloy which was treated by heat treatment with the same processing time. The electropulsing enhanced the nucleation rate of recrystallization for rolled ZK60 alloy and then accelerated the process of recrystallization.
38 Influence of heat-treatment parameters on the epitaxial growth of LZO film deposited by CSD process
2016, 45(10):2683-2686.
Abstract:
Influences of four parameters of CSD process to deposit LZO films on the epitaxial growth of the LZO films were studied. The results indicated that the intensity of (400) peak increased with increasing the heating temperature, heating time and heating rate. The results about the influence of oxygen partial pressure showed that the texture of LZO film was very sensitive to oxygen partial pressure during heat-treatment, and the influence of oxygen partial pressure on the texture of LZO film was more important than that of other parameters in order to obtain a cube-textured LZO film. The influence of heating temperature, heating time, and heating rate could be explained by the classic nucleation and growth theory. However, oxygen partial pressure had a dual role, one was to decrease the content of residual carbon in the film, which was good for the growth of LZO grains, and the other was to weaken the inhibition of the spontaneous nucleation and growth of LZO grains due to decreaseing the content of residual carbon in the film, and finally the texture of LZO film was not a cube texture. So controlling or modifying the oxygen partial pressure at the different stages of heat-treatment may be a key to improve the kinetic of LZO grains and not to influence the epitaxial growth of LZO film.
Influences of four parameters of CSD process to deposit LZO films on the epitaxial growth of the LZO films were studied. The results indicated that the intensity of (400) peak increased with increasing the heating temperature, heating time and heating rate. The results about the influence of oxygen partial pressure showed that the texture of LZO film was very sensitive to oxygen partial pressure during heat-treatment, and the influence of oxygen partial pressure on the texture of LZO film was more important than that of other parameters in order to obtain a cube-textured LZO film. The influence of heating temperature, heating time, and heating rate could be explained by the classic nucleation and growth theory. However, oxygen partial pressure had a dual role, one was to decrease the content of residual carbon in the film, which was good for the growth of LZO grains, and the other was to weaken the inhibition of the spontaneous nucleation and growth of LZO grains due to decreaseing the content of residual carbon in the film, and finally the texture of LZO film was not a cube texture. So controlling or modifying the oxygen partial pressure at the different stages of heat-treatment may be a key to improve the kinetic of LZO grains and not to influence the epitaxial growth of LZO film.
39 Effect of electropulsing treatment on the microstructure and the properties of the rolled AZ31 alloy
2016, 45(10):2687-2691.
Abstract:
In this paper, the effect of electroplsing treatment (EPT) on the microstructure evolution and the mechanical properties was studied. The recrystallization of the deformed AZ31 magnesium alloy was accelerated by using EPT with high current density and low duty ratio. EPT with different parameters was analized. The thermal and athermal effect of EPT is researched and the mechanism of the recrystallization under EPT was also revealed. The results indicated that the deformed AZ31 magnesium alloy recrystallized under the EPT for 5.5 minutes. After EPT with a pluse-width of 20 μs, a current density of 3.508×109 A/m2, a duty ratio of 0.002 and a processing time of 5min, the average grain size of AZ31 alloy is refined from 72 μm to 2 μm, the tensile strength is 295 MPa, and the elongation is 20%.
In this paper, the effect of electroplsing treatment (EPT) on the microstructure evolution and the mechanical properties was studied. The recrystallization of the deformed AZ31 magnesium alloy was accelerated by using EPT with high current density and low duty ratio. EPT with different parameters was analized. The thermal and athermal effect of EPT is researched and the mechanism of the recrystallization under EPT was also revealed. The results indicated that the deformed AZ31 magnesium alloy recrystallized under the EPT for 5.5 minutes. After EPT with a pluse-width of 20 μs, a current density of 3.508×109 A/m2, a duty ratio of 0.002 and a processing time of 5min, the average grain size of AZ31 alloy is refined from 72 μm to 2 μm, the tensile strength is 295 MPa, and the elongation is 20%.
2016, 45(10):2692-2696.
Abstract:
The tungsten coating layers on diamond are obtained by a micro vacuum evaporation diffusion method, and the diamond copper composites are prepared by vacuum pressureless infiltration. The plating layer structure is analyzed with XRD, and the surface morphology of plating layer and the diamond/copper interface morphology in the composite materials are observed by scanning electron microscopy. The results indicate that the surface of diamond coated tungsten layer improves the wettability of the matrix. The thermal conductivity fist increases and then decreases with the increasing coating thickness. The full uniform plating layer on the diamond/copper interface has a high heat conductance.
The tungsten coating layers on diamond are obtained by a micro vacuum evaporation diffusion method, and the diamond copper composites are prepared by vacuum pressureless infiltration. The plating layer structure is analyzed with XRD, and the surface morphology of plating layer and the diamond/copper interface morphology in the composite materials are observed by scanning electron microscopy. The results indicate that the surface of diamond coated tungsten layer improves the wettability of the matrix. The thermal conductivity fist increases and then decreases with the increasing coating thickness. The full uniform plating layer on the diamond/copper interface has a high heat conductance.
2016, 45(10):2697-2702.
Abstract:
Pt-Ni alloy nanoparticles with different atomic ratios of Pt to Ni (1:3；1:1；3:1) were prepared by colloidal synthesis method with Pt(acac)2 and Ni(ac)2?4H2O as precursors, respectively, and Pt-Ni/C bi-metallic catalysts were obtained after the nanoparticles were loaded on the surface of XC-72 carbon supports, and Pt3Ni/C catalysts displayed the best catalytic activity. The peak current density of Pt3Ni/C catalyst was 42.5 mA.cm-2 at the positive scanning, which was 3.2, 5.3 and 1.2 times as high as those of PtNi/C, PtNi3/C and Pt/C catalysts, and else the anti-poisoning ability of PtNi3/C was the strongest (If/Ib was 23.5) contorted with other samplers. TEM and XRD analysis indicated that Pt-Ni bi-metallic nanoparticles are uniformly distributed with the sizes ranging from 2 to 4 nm, and XPS demonstrated that the addition of Ni changes the external electronic structure of Pt, reduces the absorption of CO on Pt and releases more Pt active sites, which was the reason for the electrocatalytic activity and anti-poisoning ability of Pt-Ni/C catalyst improved.
Pt-Ni alloy nanoparticles with different atomic ratios of Pt to Ni (1:3；1:1；3:1) were prepared by colloidal synthesis method with Pt(acac)2 and Ni(ac)2?4H2O as precursors, respectively, and Pt-Ni/C bi-metallic catalysts were obtained after the nanoparticles were loaded on the surface of XC-72 carbon supports, and Pt3Ni/C catalysts displayed the best catalytic activity. The peak current density of Pt3Ni/C catalyst was 42.5 mA.cm-2 at the positive scanning, which was 3.2, 5.3 and 1.2 times as high as those of PtNi/C, PtNi3/C and Pt/C catalysts, and else the anti-poisoning ability of PtNi3/C was the strongest (If/Ib was 23.5) contorted with other samplers. TEM and XRD analysis indicated that Pt-Ni bi-metallic nanoparticles are uniformly distributed with the sizes ranging from 2 to 4 nm, and XPS demonstrated that the addition of Ni changes the external electronic structure of Pt, reduces the absorption of CO on Pt and releases more Pt active sites, which was the reason for the electrocatalytic activity and anti-poisoning ability of Pt-Ni/C catalyst improved.
2016, 45(10):2703-2709.
Abstract:
The effect of cooling rate after β phase heat treatment on the nodular corrosion resistance of Zircaloy-4 specimens was investigated by autoclave tests in superheated steam at 500 ℃/10.3 MPa. The nonuniform nodular corrosion resistance of Zircaloy-4 plates produced in factory was also studied. The results indicate that, the precipitation of Zr(Fe,Cr)2 second phase particles along α-Zr grain boundaries occurred with the decrease of cooling rate after β phase heating. It means that supersaturated solid solution contents of Fe and Cr alloying elements in α-Zr matrix were reduced with the decrease of cooling rate after β phase heating, and the nodular corrosion resistance of Zircaloy-4 specimens after cold rolling and recrystallization annealing was also degraded. It is considered that the variance of cooling rate at different parts of the same slab during β phase quenching in industrial production was contributed to the nonuniform nodular corrosion resistance of Zircaloy-4 plates.
The effect of cooling rate after β phase heat treatment on the nodular corrosion resistance of Zircaloy-4 specimens was investigated by autoclave tests in superheated steam at 500 ℃/10.3 MPa. The nonuniform nodular corrosion resistance of Zircaloy-4 plates produced in factory was also studied. The results indicate that, the precipitation of Zr(Fe,Cr)2 second phase particles along α-Zr grain boundaries occurred with the decrease of cooling rate after β phase heating. It means that supersaturated solid solution contents of Fe and Cr alloying elements in α-Zr matrix were reduced with the decrease of cooling rate after β phase heating, and the nodular corrosion resistance of Zircaloy-4 specimens after cold rolling and recrystallization annealing was also degraded. It is considered that the variance of cooling rate at different parts of the same slab during β phase quenching in industrial production was contributed to the nonuniform nodular corrosion resistance of Zircaloy-4 plates.
43 Flow Behaviors and Stress Analysis of Materials during Canned Hot Extrusion Process of PM Superalloy
2016, 45(10):2710-2716.
Abstract:
Flow behaviors of the core and the canning during canned hot extrusion have been investigated using FEM and validated by industrial test. The results show that several stages of the extrude process could be concluded based on both the extrusion force vs. stroke curve and the features of materials flow behaviors, which were simulated by FEM. The stage of the core steady flow is of more importance, in which the length and the radius of the core directly determine the bar yield and extrusion ratio. The stress analyses were made in typical locations in cross section of the billet and thus vector distribution of stress state were pictured and the strain type and complexity were quantitatively characterized using Lode parameters. Furthermore, the method calculating the extrusion ratio was proposed and the effect of yield stress on flow behaviors and extrusion ratio was illuminated. The comparison result shows that the thickness of the canning obtained by FEM is well agreement with that in industrial test.
Flow behaviors of the core and the canning during canned hot extrusion have been investigated using FEM and validated by industrial test. The results show that several stages of the extrude process could be concluded based on both the extrusion force vs. stroke curve and the features of materials flow behaviors, which were simulated by FEM. The stage of the core steady flow is of more importance, in which the length and the radius of the core directly determine the bar yield and extrusion ratio. The stress analyses were made in typical locations in cross section of the billet and thus vector distribution of stress state were pictured and the strain type and complexity were quantitatively characterized using Lode parameters. Furthermore, the method calculating the extrusion ratio was proposed and the effect of yield stress on flow behaviors and extrusion ratio was illuminated. The comparison result shows that the thickness of the canning obtained by FEM is well agreement with that in industrial test.
2016, 45(10):2717-2722.
Abstract:
Abstract: As a new kind of one-dimension thermoelectric materials, silicon nanowires(SiNWs) have been researched widely in recent years due to its excellent electrical and thermal properties. Theoretically, it is feasible to reduce the lattice thermal conductivity of bulk materials and keep its electrical conductivity as well by embedding SiNWs into the matrix as second phase. In this paper 2at% Bi doped SiNWs-Mg2Si powder was prepared by means of the solution method and consolidated subsequently, and the influence of silicon nanowires on the thermoelectric performance of the Bi-doped Mg2Si matrix was studied. It is indicated that the electrical conductivity of the materials decreased greatly, and the Seebeck coefficient remained roughly the same, and the thermal conductivity reduced a small amount. With the increase of the dosage of SiNWs, the electrical conductivity furtherly decreased, and the Seebeck coefficient slightly improved, and the thermal conductivity had a rising trend. The sample with 0.1at% SiNWs embedded obtained a highest ZT value of 0.5 at 800K.
Abstract: As a new kind of one-dimension thermoelectric materials, silicon nanowires(SiNWs) have been researched widely in recent years due to its excellent electrical and thermal properties. Theoretically, it is feasible to reduce the lattice thermal conductivity of bulk materials and keep its electrical conductivity as well by embedding SiNWs into the matrix as second phase. In this paper 2at% Bi doped SiNWs-Mg2Si powder was prepared by means of the solution method and consolidated subsequently, and the influence of silicon nanowires on the thermoelectric performance of the Bi-doped Mg2Si matrix was studied. It is indicated that the electrical conductivity of the materials decreased greatly, and the Seebeck coefficient remained roughly the same, and the thermal conductivity reduced a small amount. With the increase of the dosage of SiNWs, the electrical conductivity furtherly decreased, and the Seebeck coefficient slightly improved, and the thermal conductivity had a rising trend. The sample with 0.1at% SiNWs embedded obtained a highest ZT value of 0.5 at 800K.
Lin Li
,
Zhao Beijun
,
Zhu Shifu
,
He Zhiyu
,
Chen Baojun
,
Sun Ning
,
Huang Wei
,
Yang Denghui
,
Zhong Yikai
,
Zhu Pu
2016, 45(10):2723-2728.
Abstract:
A CdSiP2 (CSP) crystal was grown by the modified Vertical Bridgman method. Four wafers which were cut from the crystal with the [001] direction and annealed under four different atmospheres, i. e. vacuum, cover-up with CSP polycrystalline powder, P/Cd (atomic ratio of 2:1) and Cd atmosphere. Then, Energy Disperse X-ray Spectroscopy, Fourier Transform Infrared Spectrophotometer and the Mapping System of Infrared Microscope were employed to analyze the properties of the CdSiP2 wafers before and after annealing, including the elementary composition, infrared absorption coefficients and infrared transmission uniformity. The measurement results show that all the stoichiometric deviation and infrared absorption coefficients are reduced, and infrared transmission uniformity of CSP wafers are improved to different extent after annealing. For the infrared absorption coefficients in the range of 1.29-2.00 μm, the most obvious decrease is due to annealing under cover-up with CSP polycrystalline powder. Meanwhile, the wafer treaded by this method also obtained the best result for infrared transmission uniformity in 1.92-1.98 μm with the increase of 14.06%. The wafer annealed under the Cd atmosphere has the lowest infrared absorption coefficients in 2.00-6.50 μm among the four wafers, and has the most obvious improvement for the infrared transmission uniformity in 2.70-2.78 μm with the increase of 17.43%. The main factors resulting in nonuniformity absorption in the wavebands mentioned above and corresponding effective annealing processes will analyze in this work.
A CdSiP2 (CSP) crystal was grown by the modified Vertical Bridgman method. Four wafers which were cut from the crystal with the [001] direction and annealed under four different atmospheres, i. e. vacuum, cover-up with CSP polycrystalline powder, P/Cd (atomic ratio of 2:1) and Cd atmosphere. Then, Energy Disperse X-ray Spectroscopy, Fourier Transform Infrared Spectrophotometer and the Mapping System of Infrared Microscope were employed to analyze the properties of the CdSiP2 wafers before and after annealing, including the elementary composition, infrared absorption coefficients and infrared transmission uniformity. The measurement results show that all the stoichiometric deviation and infrared absorption coefficients are reduced, and infrared transmission uniformity of CSP wafers are improved to different extent after annealing. For the infrared absorption coefficients in the range of 1.29-2.00 μm, the most obvious decrease is due to annealing under cover-up with CSP polycrystalline powder. Meanwhile, the wafer treaded by this method also obtained the best result for infrared transmission uniformity in 1.92-1.98 μm with the increase of 14.06%. The wafer annealed under the Cd atmosphere has the lowest infrared absorption coefficients in 2.00-6.50 μm among the four wafers, and has the most obvious improvement for the infrared transmission uniformity in 2.70-2.78 μm with the increase of 17.43%. The main factors resulting in nonuniformity absorption in the wavebands mentioned above and corresponding effective annealing processes will analyze in this work.
2016, 45(10):2729-2733.
Abstract:
A method for the determination of Vanadium in Vanadium-Aluminium master alloys by KMnO4 -Ferrous titration method is presented .The sample was digested by H2SO4-H3PO4-HNO3. The influence of the method for sample digestion; the amount of KMnO4 and NaNO2; the interference of co-existence elements were discussed so as to confirm the best condition. The proposed method was applied to determine the Vanadium contents in six Vanadium-Aluminium master alloy samples whose Vanadium content was different from 49.45% to 83.33%. The results showed that the relative standard deviations(n=11) were all about 0.2%, and the recoveries were in the range of 98.2%~102.5%.Compared with 7 different laboratories , the results were consistent without significant deviation. This method has the advantages of fast，accurate and a wide analytical range. It is suitable for determination Vanadium in Vanadium-Aluminium master alloys.
A method for the determination of Vanadium in Vanadium-Aluminium master alloys by KMnO4 -Ferrous titration method is presented .The sample was digested by H2SO4-H3PO4-HNO3. The influence of the method for sample digestion; the amount of KMnO4 and NaNO2; the interference of co-existence elements were discussed so as to confirm the best condition. The proposed method was applied to determine the Vanadium contents in six Vanadium-Aluminium master alloy samples whose Vanadium content was different from 49.45% to 83.33%. The results showed that the relative standard deviations(n=11) were all about 0.2%, and the recoveries were in the range of 98.2%~102.5%.Compared with 7 different laboratories , the results were consistent without significant deviation. This method has the advantages of fast，accurate and a wide analytical range. It is suitable for determination Vanadium in Vanadium-Aluminium master alloys.
2016, 45(10):2734-2740.
Abstract:
The hardness of the alloy surface after carburizing increases by 2.84 times. Through 1 h, 2 h, and 3 h treating,the tensile strength and nonproportional extension strength are similar to those of the original sample. After the three heat treatment (without carburized layer) elongation and reduction of area on the cross section are better than those of the original sample, but the sample with carburized layer are heavily decreased, and with the time extension, the elongation and the reduction of area decline. In the tensile process, the outer surface layer, covered with ring-shaped cracks, flakes off gradually. The cracks are increased from the root to the middle. There are small cracks on the root while the cracks become wider and larger in the middle. The cracks mainly concentrate near the fracture, and a few on the root. The fracture of the heat-treated TC4 sample is plastic fracture, and the dislocation slip plays an important role in the fracture process. The layer close to the outer surface of the sample shows brittle fracture characteristics, the core is of plastic fracture, and the fracture direction can be determined by the fracture morphology.
The hardness of the alloy surface after carburizing increases by 2.84 times. Through 1 h, 2 h, and 3 h treating,the tensile strength and nonproportional extension strength are similar to those of the original sample. After the three heat treatment (without carburized layer) elongation and reduction of area on the cross section are better than those of the original sample, but the sample with carburized layer are heavily decreased, and with the time extension, the elongation and the reduction of area decline. In the tensile process, the outer surface layer, covered with ring-shaped cracks, flakes off gradually. The cracks are increased from the root to the middle. There are small cracks on the root while the cracks become wider and larger in the middle. The cracks mainly concentrate near the fracture, and a few on the root. The fracture of the heat-treated TC4 sample is plastic fracture, and the dislocation slip plays an important role in the fracture process. The layer close to the outer surface of the sample shows brittle fracture characteristics, the core is of plastic fracture, and the fracture direction can be determined by the fracture morphology.
2016, 45(10):2741-2745.
Abstract:
The influences of different oxidation time on surface morphology, thickness, elemental distribution and phase composition of micro-arc oxidation coatings on ZL205A was studied. The results show that with the increase of oxidation time, the number of micro-pores decreases while the size of micro-pores,the thickness increase. The content of Al, Si has little changes, O, P element did not change significantly. The MAO coating are mainly composed of α- Al2O3 and Mullite(Al6Si2O13), with increasing oxidation time, the content of α- Al2O3 and Mullite increased,the Mullite phase mainly generated by the anode reaction product of SiO2 and Al2O3.
The influences of different oxidation time on surface morphology, thickness, elemental distribution and phase composition of micro-arc oxidation coatings on ZL205A was studied. The results show that with the increase of oxidation time, the number of micro-pores decreases while the size of micro-pores,the thickness increase. The content of Al, Si has little changes, O, P element did not change significantly. The MAO coating are mainly composed of α- Al2O3 and Mullite(Al6Si2O13), with increasing oxidation time, the content of α- Al2O3 and Mullite increased,the Mullite phase mainly generated by the anode reaction product of SiO2 and Al2O3.
2016, 45(10):2746-2751.
Abstract:
Abstract: Bidirectional cyclic bending technology(BCBT) had been used to improve the microstructure and texture and mechanical properties of AZ31 magnesium alloy sheet. When AZ31 Magnesium alloy sheet deformec by BCBT, the recrystallization had occurred in twins boundary, and across area between twins boundary and crystal boundary, and across area between twins and twins. And grain size was less than twins width. When deformation temperature of BCBT was 523K, the recrystallization nucleation had occurred in crystal boundary and grown up quickly. When deformation temperature was 483K and deformation process was 3 times, basal texture of AZ31 magnesium alloy sheet was weakened, and texture intensity was reduced from 9.59 to 3.54, and average grain size was 12.2μm，and elongation ratio was 17.1% at room temperature. .
Abstract: Bidirectional cyclic bending technology(BCBT) had been used to improve the microstructure and texture and mechanical properties of AZ31 magnesium alloy sheet. When AZ31 Magnesium alloy sheet deformec by BCBT, the recrystallization had occurred in twins boundary, and across area between twins boundary and crystal boundary, and across area between twins and twins. And grain size was less than twins width. When deformation temperature of BCBT was 523K, the recrystallization nucleation had occurred in crystal boundary and grown up quickly. When deformation temperature was 483K and deformation process was 3 times, basal texture of AZ31 magnesium alloy sheet was weakened, and texture intensity was reduced from 9.59 to 3.54, and average grain size was 12.2μm，and elongation ratio was 17.1% at room temperature. .
2016, 45(10):2752-2756.
Abstract:
The superconducting materials have been widely used in the high-tech fields, e.g. high-energy physics, controlled thermonuclear fusion, energy storage device and maglev etc. The NbTi alloy as a typical low-temperature superconducting material occupies a very important place. By simulated calculation with DEFORM, the dynamic behavior of the forging process has been studied. Further, combined with practical process, the evolution of the microstructure has been obtained, and the preparation technology of the NbTi alloy bars has been acquired. According to the results of simulated calculation, it indicates that the NbTi alloy is deformed homogeneously under a small deformation range, the 1/3 length press and the reversal stretch, which eliminates effectively the deformation dead zone. This optimized technology used to produce NbTi alloy bars, which is well satisfied with the related requirement, has been perfomed in industrial production.
The superconducting materials have been widely used in the high-tech fields, e.g. high-energy physics, controlled thermonuclear fusion, energy storage device and maglev etc. The NbTi alloy as a typical low-temperature superconducting material occupies a very important place. By simulated calculation with DEFORM, the dynamic behavior of the forging process has been studied. Further, combined with practical process, the evolution of the microstructure has been obtained, and the preparation technology of the NbTi alloy bars has been acquired. According to the results of simulated calculation, it indicates that the NbTi alloy is deformed homogeneously under a small deformation range, the 1/3 length press and the reversal stretch, which eliminates effectively the deformation dead zone. This optimized technology used to produce NbTi alloy bars, which is well satisfied with the related requirement, has been perfomed in industrial production.
