医用β-Ti30Nb13Zr0.5Fe合金的热变形行为

Hot deformation behaviors of biomedical β-Ti30Nb13Zr0.5Fe alloy

利用热模拟实验机对Ti30Nb13Zr0.5Fe(质量分数,%)医用钛合金在温度700～850℃、变形速率10^(-3)～10 s^(-1)范围内进行等温热压缩试验,观察变形后钛合金的显微组织,并根据动力学分析确定合金β相区热变形方程、应力指数n和激活能Q。结果表明:温度变化不改变σ—ε曲线特征;应变速率对变形行为的影响较大,(?)为1～10 s^(-1)时,出现流变不稳定性;(?)为10^(-2)～1 s^(-1)时,组织发生β相再结晶和动态回复;当θ>800℃、(?)<10^(-2) s^(-1)时,组织发生β相连续再结晶,导致晶粒粗化;合金β相区变形应力指数n和激活能Q分别为4.5和195kJ/mol;综合考虑可热加工性和组织细化因素,温度为700～800℃、应变速率为10^(-3)～10^(-1)s^(-1)是良性热加工区域。

The hot deformation behaviors of Ti30Nbl3Zr0.5Fe （mass fraction, %） alloy were studied by thermal-simulator in the temperature range of 700-850 ℃ and strain rate range of 10^-3-10 s^-1. The hot deformation equation, stress exponential n and deformation activation energy Q were established according to the dynamical analysis. The microstructures were observed by optical microscopy. The results indicate that the variation of deformation temperature doesn＇t change the characteristics of true stress--strain curves, but the variation of strain rate has crucial effect on the deformation behaviors. The instable flow happens at strain rate of 1-10 s^-1, the dynamic recrystallization and dynamic recovery of β phase occur at strain rate of 10^-2-1 s^-1. And the continual recrystallization and grain coarsening occur at strain rate less than 10^-2 s^-1 and temperature higher than 800 ℃. The stress exponential n and deformation activation energy Q of fl phase are 4.5 and 195 kJ/mol, respectively. Considering workability and microstructure refining, the optimum conditions of hot deformation for Ti30Nbl3Zr0.5Fe alloy are the temperature range of 700-800 ℃ and strain rate range of 10^-3-10^-1 s^-1.