冲击加载条件下AZ31B镁合金变形孪晶的微观特征

Microstructure Characterization of Twinning Under Impact Loading for AZ31B Magnesium Alloys

采用分离式Hopkinson压杆(SHPB)对AZ31B热轧板材沿轧向进行冲击实验,加载应变率约为1 200 s-1.利用金相显微镜和透射电子显微镜观察微观组织特征。结果表明:在应变量约为0.003的条件下,压缩孪生{101-1}/<101-2>与拉伸孪生{11-02}/<1 1-01>均为孪生塑性变形机制,这与准静态加载下单一的拉伸孪生机制不同。孪晶内部的微观特征演化过程包括:1)平行排列基面层错的出现;2)与孪晶界成特定角度平行排列位错线的形成;3)位错胞的产生。

Dynamic mechanical properties of AZ31B sheet were carried out in compression along rolling direction using split Hopkinson bar（SHPB） at the strain rate of 1 200 s-1.Post-mortem observations were conducted using optical microscope and transmission electron microscope.The results show that both {10 11}/10 1-2 and {1 1-02}/10 1-1 twinning are the plastic deformation mechanisms at the strain of 0.003,which is different from the {10 12}/10 1-1 twinning deformation mechanism under quasi-static loading condition.The evolution of microstructure inside twinning consists of parallel basal stacking faults,parallel dislocation arrays of different orientations to twin boundary and dislocation cells.