ZK60镁合金高应变速率压缩变形的流变行为及显徽组织

在250-400℃的温度范围和0.1-50 s^-1的应变速率范围内对ZK60合金进行压缩变形，对其流变行为和显微组织进行研究。结果表明，在低应变速率（0.1-1 s^-1）下压缩变形时，再结晶主要发生在初始晶界上；在高应变速率（10-50 s^-1）下压缩变形时，再结晶同时在初始晶界和孪晶上发生。合金在应变速率10-50 s^-1和温度250-350℃的变形条件下获得均匀、细小的再结晶组织。因此，合金的最佳热加工工艺范围为应变速率10-50 s^-1、变形温度250-350℃。高应变速率压缩变形条件下的孪生诱发动态再结晶过程分三步，首先，高位错密度孪晶分割初始晶粒；然后，孪晶内的位错发生重排形成亚晶；最后，随着应变的增加而形成再结晶晶粒。

Flow behavior and microstructure of ZK60 magnesium alloy compressed at high strain rate

Flow behavior and microstructure of a homogenized ZK60 magnesium alloy were investigated during compression in the temperature range of 250-400 ℃ and the strain rate range of 0.1-50 s^-1. The results showed that dynamic recrystallization （DRX） developed mainly at grain boundaries at lower strain rate （0.1-1 s^-1）, while in the case of higher strain rate （10-50 s^-1）, DRX occurred extensively both at twins and grain boundaries at all temperature range, especially at temperature lower than 350 ℃, which resulted in a more homogeneous microstructure than that under other deformation conditions. The DRX extent determines the hot workability of the workpiece, therefore, hot deformation at the strain rate of 10-50 s^-1 and in the temperature range of 250-350 ℃ was desirable for ZK60 alloy. Twin induced DRX during high strain rate compression included three steps. Firstly, twins with high dislocation subdivided the initial grain, then dislocation arrays subdivided the twins into subgrains, and after that DRX took place with a further increase of strain.