High Temperature Deformation Behaviors for α+β Type Biomedical Titanium Alloy Ti-6Al-7Nb
Isothermal hot compression tests were carried out in the temperature range 750-900℃ and strain rate range 0.001-10s-1 for implant biomedical Ti-6Al-7Nb alloy to obtain the hot deformation behaviors. Hot tensile tests were conducted to examine the hot ductility. Deformed microstructures were observed by optical and electron transmission microscope. The stress-strain curves in hot compression tests behave the characteristics of flow softening. The flow softening at =0.001~0.1s-1 is caused by dynamic recrystallization of a phase. Especially, the full dynamic recrystallization occurs at 750℃ and strain rate 0.01 s-1, which produces refined grains with the size of 1~2μm. No dynamic recrystallization was found at strain rate of 1~10s –1. Here the flow softening is caused by the adiabatic effect and dynamic recovery. According to the kinetic rate equation, the apparent activation energies at 750℃, 800℃, 850℃ and 900℃ are calculated to be 209 kJ/mol, 196 kJ/mol, 194 kJ/mol and 130kJ/mol, respectively. Combining the kinetic analysis with the observation of deformed microstructures, it is concluded that at lower temperature (750-850℃) and slow strain rate (0.001~0.1s-1) the deformation is mainly controlled by recrystallization and grain boundary slide of α phase. At higher temperature (900℃) or large strain rate (1~10s –1) the dynamic recovery in b phase is rate-controlling step. Considering workability and microstructural control, the optimum hot deformation conditions are determined in the temperature range 750-850℃ and strain rate range 0.01-0.1s-1.
biomedical titanium alloy hot compression microstructure deformation mechanisms
WenFang CUI Zhe JIN AiHong GUO Lian ZHOU
Key Laboratory of Anisotropy and Texture of Materials (Ministry of Education),Northeastern Universit Northwest Institute for Non-ferrous Metal Research, Xi’an 710016, China
国际会议
郑州
英文
2007-10-23（万方平台首次上网日期，不代表论文的发表时间）