中文摘要：

基于晶体塑性理论，建立了一个考虑滑移、形变孪晶以及孪晶内二次滑移的镁单晶弹-黏塑性细观本构模型，并在有限元软件 ABAQUS 的用户子程序 UMAT 中数值实现。利用该模型对镁单晶的室温平面压缩试验进行了模拟，研究了不同加载取向下镁单晶变形机制的演化规律。结果表明：镁单晶的变形机制与取向密切相关，其力学行为表现出强烈的各向异性特征；拉伸孪晶在特定取向下能够提供沿晶粒 c 方向伸长的变形，并引起晶粒的重取向；在某些变形状态下，当拉伸孪晶达到饱和体积分数后，孪晶内会出现二次滑移。

英文摘要：

Based on crystal plasticity theory ,a mesoscale elastic-viscoplastic constitutive model for Mg single crystal was proposed ,including slip ,deformation twinning and secondary slip in the twinning areas . The model was implemented in ABAQUS by UMAT .Plane strain compression experiments of Mg single crystal were simulated .The evolution of deformation mechanisms under different loading orientations was studied . The results show that the deformation mechanisms of Mg single crystal are orientation-dependent ,and its mechanical behaviors show strong anisotropy .Tension twinning can induce extension along c-axis and reorientation of the Mg single crystal . After the volume fraction of tension twinning reaches the saturation value , the secondary slip is found in the twinning areas under some loading conditions .