压缩条件下AZ31镁合金第Ⅱ阶段加工硬化

Second-stage strain hardening of AZ31 magnesium alloy in compression

在温度为25℃~300℃、应变速率为3×10^(-2)s^(-1)~10^(-4)s^(-1)的条件下,对挤压态的AZ31镁合金沿挤压方向进行了压缩试验,试验研究了加工硬化率随应力的变化关系,以及产生第Ⅱ阶段加工硬化的原因。结果表明,在一定温度及应变速率范围内,加工硬化率随应力增加而增加,当加工硬化率达到峰值时即出现第Ⅱ阶段加工硬化。产生第Ⅱ阶段加工硬化的主要原因是压缩过程中,镁合金组织产生了{1012}拉伸孪晶,随着孪晶数量增加,大量孪晶界会阻碍位错运动,造成加工硬化率升高。

A compression test along the extrusion direction of AZ31 magnesium alloy spec- imen was carried out at the temperature ranging from 25℃to 300℃ and the strain rate from 3 × 10-2 s-1 to 10-4 s-1 ,as a way to investigate the strain hardening rate as a function of stress and the mechanism of second-stage strain hardening. The results show that strain hard- ening rate increases with stress and the second-stage strain hardening occurs when the peak strain hardening rate is reached at a certain range of temperature and strain rate. The main cause of second-stage strain hardening is that a tension twinning { 101-2 } is created in the mi- crostructure of compression specimens, the motion of dislocations is blocked when large amount of twinning appear, and then strain hardening rate goes up.