The thermomechanical coupling simulation of the isothermal equal channel angular pressing（ECAP） of Ti-6Al-4V alloy was conducted.The effect of processing parameters,ECAP pass number and the residual billet on the ef...The thermomechanical coupling simulation of the isothermal equal channel angular pressing（ECAP） of Ti-6Al-4V alloy was conducted.The effect of processing parameters,ECAP pass number and the residual billet on the effective strain,stress and temperature distribution was investigated.Based on the coupling simulation results,it is found that the shear factor,ram speed,deformation temperature,channel intersection angle and residual billet significantly affect the ECAP deformation behaviors.Meanwhile,the experimental study of the isothermal ECAP process of Ti-6Al-4V alloy using route C,in which the repeated rotation angle around the longitudinal billet axis before reinsertion in the die was 180°,were conducted at a deformation temperature of 750°C,a ram speed of 0.3 mm·s-1,an outer arc of curvature of 60° and a channel intersection angle of 120°.Furthermore,a large amount of recrystallization occurs and some prior α phase grains grow in the post-ECAP process of Ti-6Al-4V alloy.The yield strength of post-ECAP Ti-6Al-4V alloy increases compared with that of as-received Ti-6Al-4V alloy.展开更多
According to the construction principle of B-spline, a formula of surface construction for airfoil blade with the given points has been derived. Meanwhile, the surface construction system for airfoil blade in practice...According to the construction principle of B-spline, a formula of surface construction for airfoil blade with the given points has been derived. Meanwhile, the surface construction system for airfoil blade in practice as well as menus for the system have been constructed with the help of the commercial software (AutoCAD R14). The result in this paper is helpful for CAD/CAM of airfoil blades.展开更多
Superplastically free bulging of duralumin LY 12CZ (approximately corre-sponding to ASTM 2024) without any pretreatment has been investigated under an ex-ternal strong electnc field. The experimental results show that...Superplastically free bulging of duralumin LY 12CZ (approximately corre-sponding to ASTM 2024) without any pretreatment has been investigated under an ex-ternal strong electnc field. The experimental results show that the electric field makesthe relative maximum height of the superplastically formed parts increase by 15%.Moreover, the determination of grain size and aspect ratio of grains and themetallographic observation of cavities have also been done. These results have verifiedthat the electric field improves the superplasticity during superplastically free bulging ofduralumin LY12CZ and that it is possible to utilize superplastic defonnation with elec-tric field in industrial practice.展开更多
The dynamic conditions for plastic deformation mechanism,surface source mechanism,interface source mechanism and creep mechanism in the diffusion bonding process are proposed.Based on these dynamic conditions,a model ...The dynamic conditions for plastic deformation mechanism,surface source mechanism,interface source mechanism and creep mechanism in the diffusion bonding process are proposed.Based on these dynamic conditions,a model for void closure in the diffusion bonding process is derived.The effects of diffusion bonding parameters on the bonding mechanisms are analyzed.For the diffusion bonding process of TC4 alloy,at a low diffusion bonding temperature or pressure,or for a short time,the interface source mechanism plays a main role.But,the creep mechanism is the dominant mechanism and operates until the diffusion bonding is fulfilled.As the diffusion bonding time increases,the surface source and interface source mechanism enhance and then stop at a certain stage of diffusion bonding,while the creep mechanism enhances continuously.As the diffusion bonding temperature or pressure increases,the interface source mechanism weakens and the other mechanisms enhance.The maximum and average errors between the calculated and the experimental results in the diffusion bonding for TC4 alloy are 12.86% and 5.79%,respectively.展开更多
The continuous dynamic recrystallization(CDRX) through a progressive transformation of a subgrain structure into a grain structure with the increasing of misorientation occurred in the hot deformation of titanium allo...The continuous dynamic recrystallization(CDRX) through a progressive transformation of a subgrain structure into a grain structure with the increasing of misorientation occurred in the hot deformation of titanium alloy. A grain size model for CDRX of titanium alloy in hot deformation considering work hardening effect, dynamic softening effect and non-homogeneous deformation effect was established. The β grain size was described as functions of the deformation temperature, strain rate and strain by using the dislocation density as an internal state variable. The inside dislocation storage and dislocation annihilation,which respectively resulted from work hardening effect and dynamic softening effect, were described by the Kocks-Mecking and Picu-Majorell theories correspondingly. The dislocation density rate associated with non-homogeneous deformation effect was done in terms of the Ashby theory. The material constants in the present model were determined via genetic algorithm(GA)-based objective optimization technique. Applying the grain size model to the hot deformation of Ti-5Al-2Sn-2Zr-4Mo-4Cr, the maximum difference between the calculated and experimental β grain size was 8.2%. Moreover, the effect of deformation temperature and strain rate on the β grain size in the hot deformation of Ti-5Al-2Sn-2Zr-4Mo-4Cr was calculated, indicating that the β grain size increased with the increasing of deformation temperature and the decreasing of strain rate.展开更多
There exists an interaction between microstructural evolution and deformation behavior in high temperature deformation of titanium alloys. And the microstruc- ture of titanium alloys is very sensitive to the process p...There exists an interaction between microstructural evolution and deformation behavior in high temperature deformation of titanium alloys. And the microstruc- ture of titanium alloys is very sensitive to the process parameters of plastic de- formation process. In this paper, on the basis of plastic deformation mechanism of metals and alloys, a microstructural model including dislocation density rate equa- tion and grain growth rate equation is established with the dislocation density rate being an internal state variable. Applying the model to the high temperature de- formation process of Ti60 titanium alloy, the average relative errors of grain sizes between the experiments and the predictions are 9.47% for sampled data, and 13.01% for non-sampled data.展开更多
基金supported by the National Natural Science Foundation of China (No.50975234)the Northwestern Polytechnical University Foundation for Research (No.NPU-FFR-006)
文摘The thermomechanical coupling simulation of the isothermal equal channel angular pressing（ECAP） of Ti-6Al-4V alloy was conducted.The effect of processing parameters,ECAP pass number and the residual billet on the effective strain,stress and temperature distribution was investigated.Based on the coupling simulation results,it is found that the shear factor,ram speed,deformation temperature,channel intersection angle and residual billet significantly affect the ECAP deformation behaviors.Meanwhile,the experimental study of the isothermal ECAP process of Ti-6Al-4V alloy using route C,in which the repeated rotation angle around the longitudinal billet axis before reinsertion in the die was 180°,were conducted at a deformation temperature of 750°C,a ram speed of 0.3 mm·s-1,an outer arc of curvature of 60° and a channel intersection angle of 120°.Furthermore,a large amount of recrystallization occurs and some prior α phase grains grow in the post-ECAP process of Ti-6Al-4V alloy.The yield strength of post-ECAP Ti-6Al-4V alloy increases compared with that of as-received Ti-6Al-4V alloy.
文摘According to the construction principle of B-spline, a formula of surface construction for airfoil blade with the given points has been derived. Meanwhile, the surface construction system for airfoil blade in practice as well as menus for the system have been constructed with the help of the commercial software (AutoCAD R14). The result in this paper is helpful for CAD/CAM of airfoil blades.
文摘Superplastically free bulging of duralumin LY 12CZ (approximately corre-sponding to ASTM 2024) without any pretreatment has been investigated under an ex-ternal strong electnc field. The experimental results show that the electric field makesthe relative maximum height of the superplastically formed parts increase by 15%.Moreover, the determination of grain size and aspect ratio of grains and themetallographic observation of cavities have also been done. These results have verifiedthat the electric field improves the superplasticity during superplastically free bulging ofduralumin LY12CZ and that it is possible to utilize superplastic defonnation with elec-tric field in industrial practice.
基金supported by the National Natural Science Foundation of China (Grant No. 50975234)
文摘The dynamic conditions for plastic deformation mechanism,surface source mechanism,interface source mechanism and creep mechanism in the diffusion bonding process are proposed.Based on these dynamic conditions,a model for void closure in the diffusion bonding process is derived.The effects of diffusion bonding parameters on the bonding mechanisms are analyzed.For the diffusion bonding process of TC4 alloy,at a low diffusion bonding temperature or pressure,or for a short time,the interface source mechanism plays a main role.But,the creep mechanism is the dominant mechanism and operates until the diffusion bonding is fulfilled.As the diffusion bonding time increases,the surface source and interface source mechanism enhance and then stop at a certain stage of diffusion bonding,while the creep mechanism enhances continuously.As the diffusion bonding temperature or pressure increases,the interface source mechanism weakens and the other mechanisms enhance.The maximum and average errors between the calculated and the experimental results in the diffusion bonding for TC4 alloy are 12.86% and 5.79%,respectively.
基金supported by the National Natural Science Foundation of China(Grant No.51475375)the Fund of the State Key Laboratory of Solidification Processing in NWPU(Grant No.KP201513)
文摘The continuous dynamic recrystallization(CDRX) through a progressive transformation of a subgrain structure into a grain structure with the increasing of misorientation occurred in the hot deformation of titanium alloy. A grain size model for CDRX of titanium alloy in hot deformation considering work hardening effect, dynamic softening effect and non-homogeneous deformation effect was established. The β grain size was described as functions of the deformation temperature, strain rate and strain by using the dislocation density as an internal state variable. The inside dislocation storage and dislocation annihilation,which respectively resulted from work hardening effect and dynamic softening effect, were described by the Kocks-Mecking and Picu-Majorell theories correspondingly. The dislocation density rate associated with non-homogeneous deformation effect was done in terms of the Ashby theory. The material constants in the present model were determined via genetic algorithm(GA)-based objective optimization technique. Applying the grain size model to the hot deformation of Ti-5Al-2Sn-2Zr-4Mo-4Cr, the maximum difference between the calculated and experimental β grain size was 8.2%. Moreover, the effect of deformation temperature and strain rate on the β grain size in the hot deformation of Ti-5Al-2Sn-2Zr-4Mo-4Cr was calculated, indicating that the β grain size increased with the increasing of deformation temperature and the decreasing of strain rate.
基金the National Natural Science Foundation of China (Grant No. 50475144)the NPU Foundation for Research (Grant No. NPU-FFR-006)the National Basic Research Program of China ("973") (Grant No. G20000672)
文摘There exists an interaction between microstructural evolution and deformation behavior in high temperature deformation of titanium alloys. And the microstruc- ture of titanium alloys is very sensitive to the process parameters of plastic de- formation process. In this paper, on the basis of plastic deformation mechanism of metals and alloys, a microstructural model including dislocation density rate equa- tion and grain growth rate equation is established with the dislocation density rate being an internal state variable. Applying the model to the high temperature de- formation process of Ti60 titanium alloy, the average relative errors of grain sizes between the experiments and the predictions are 9.47% for sampled data, and 13.01% for non-sampled data.
