新型超高强度Ti-20Zr-6.5Al-4V合金热变形行为及热加工图

Hot deformation behavior and processing maps of new ultra-high strength Ti-20Zr-6.5Al-4V alloy

采用Gleeble 3500热模拟实验机对Ti-20Zr-6.5Al-4V合金进行等温热压缩实验,研究该合金在变形温度为750~1050℃和变形速率为100~10-3s-1条件下的热变形行为和热加工图。研究结果表明:在β单相区,低温高应变速率时,变形初期流变曲线会产生一个显著的应力降现象,随变形温度升高和应变速率降低,应力降现象逐渐消失;高温低应变速率时,流变曲线呈现出典型的动态再结晶特征;在α+β相区,高应变速率时,变形初期流变曲线也会产生一个显著的应力降;随着应变速率降低,应力降现象逐渐消失,流变曲线呈现出连续的流变软化现象;随着应变增大,Ti-20Zr-6.5Al-4V合金在α+β双相区的热变形激活能从414.2 k J/mol降到173.8 kJ/mol,而在β单相区的热变形激活能从123.5 kJ/mol降到95.2 kJ/mol;Ti-20Zr-6.5Al-4V合金最优热加工参数范围分别为750~830℃和10-3~10-2 s-1以及925~1020℃和5.6×10-3~1.2×10^-1s^-1,最优热加工工艺参数组合为750oC和10-3s-1以及950oC,10-2s-1。

To study the hot deformation behavior and processing maps of Ti-20 Zr-6.5 Al-4 V alloy,the isothermal compression test was carried out at 750-1050°C and strain rates of 100-10-3s-1 by Gleeble 3500 thermal simulator.The results show that at low temperatures and high strain rates,a significant stress drop is observed in the initial stage of deformation in singleβphase region.With the increase of deformation temperature and decrease of strain rate,the phenomenon of stress drop is invisible.At higher temperature and lower strain rate,the flow curve illustrates a typical characterization of dynamic recrystallization.In theα+βphase region,the phenomenon of stress drop is also observed at high strain rates in the initial stage of deformation.With the decrease of strain rate,the phenomenon of stress drop disappears,and the flow curve exhibits a continuous flow softening phenomenon.With the increase of strain,the activation energy for hot deformation decreases from 123.5 to 95.2 kJ/mol in the singleβphase region,and from 414.2 kJ/mol to 243.5 kJ/mol in theα+βphase region.The optimum processing parameter ranges are determined to be 750-830℃and 10-3-10-2 s-1,and 925-1020℃and5.6×10-3-1.2×10^-1s^-1,respectively.The optimum processing parameters are evaluated to be 750 oC,10-3 s-1 and 950 oC,10-2 s-1.