高应变速率下AZ31B镁合金的压缩变形组织

Deformation microstructure of AZ31B magnesium alloy under high strain rate compression

采用分离式Hopkinson杆在应变速率为496～2120 s^-1范围对挤压态AZ31B镁合金进行了高速冲击压缩实验，并采用金相显微镜对压缩后镁合金的组织演变规律进行研究。结果表明：在不同应变速率下变形时，挤压态AZ31镁合金的应力-应变曲线几乎重合，说明AZ31B镁合金的应力对应变速率不敏感；但其显微组织变化对应变速率非常敏感，当变形速率较低时，其组织几乎全部由孪晶组成；当应变速率增加时，孪晶数量减少；在应变速率相对较低时（496S-1），镁合金变形主要以孪生方式进行；当应变速率较高时（2120S-1），除孪晶变形之外，柱面滑移和锥面滑移也可能启动以协调变形。

In order to investigate the microstructure evolution under high strain rate deformation, extruded AZ31B magnesium alloy was impacted by split Hopkinson compression bars at the strain rates of 496-2 120 s^-1. The microstructures of the specimens were observed by optical microscopy. The results show that the stress-strain curves of AZ31B magnesium alloy are almost overlap under different strain rates, implying that the stress of AZ31B magnesium is not sensitive to the strain rate. The deformation microstructure analysis demonstrates that the microstructure is sensitive to the strain rate. When the strain rate is relatively low, the microstructure is dominated by intense twinning. With increasing strain rate, the volume fraction of twinning decreases. The microstructure analysis demonstrate that at relatively low strain rate, the deformation mechanism of AZ31B magnesium alloy under impact load is twinning, while the strain rate increases to 2 120 s^-1, the prismatic slip and pyramidal slip may be active to accommodate with the deformation except twinning.