Ti60合金热变形过程中的软化机制

Softening mechanism of Ti60 alloy during hot deformation

采用Thermecmaster−Z型热加工模拟试验机对Ti60合金进行等温恒应变速率压缩实验,通过分析流动应力−应变曲线的流动特征,计算加工硬化率,观察变形微观组织,并结合变形激活能的计算,研究该合金在变形温度为850~950℃、应变速率为0.001~10 s^−1、真应变为0.51热变形条件下的软化机制。结果表明:Ti60合金在低应变速率(0.001~0.1 s^−1)和高应变速率(1~10 s^−1)区间流动应力−应变曲线分别呈现流动稳态型和流动软化型两种;加工硬化率曲线呈现无拐点特征;变形微观组织为动态回复组织,未出现动态再结晶现象;变形激活能在低应变速率区间和高应变速率区间分别为484.35 kJ/mol和500.76 kJ/mol,两者相差不大。综合这些结果可以判定,Ti60合金的软化机制以动态回复为主。

The isothermal compression tests of Ti60 alloy were conducted on the Thermecmaster-Z thermal simulator,through analyzing the flow stress-strain curve characteristics,calculating work hardening rate,observing deformation microstructure of alloy and the deformation activation energy,the softening mechanism is that deformation temperature of 850−950℃,the strain rate of 0.001−10 s^−1 and true strain of 0.51.The results show that flow stress-strain curve of Ti60 alloy presents the flow steady state under low stain rate(0.001−0.1 s^−1)and flow softening state under high stain rate(1−10 s^−1),respectively.The curve of work hardening rate shows no inflection point.The microstructure of deformation is dynamic recovery microstructure without dynamic recrystallization.The activation energy of deformation is 484.35 kJ/mol under low stain rate and 500.76 kJ/mol under high stain rate,with little difference between them.Comprehensively based on these results,it can be concluded that the softening mechanism of Ti60 alloy is mainly dynamic recovery.