中文摘要：

为了研究镁合金单晶塑性流动规律,同时考虑滑移与孪生变形机制,在晶体塑性理论基础上建立镁合金晶体本构关系.结合有限元方法,针对AZ31镁合金单晶材料的初始屈服面形状变化开展数值研究,即分别对3种双轴加载下2种平移应变2×10^-4和5×10^-4的屈服面形状进行预测.由预测结果与试验数据比较分析得出以下结论：预测的2种平移应变的屈服面形状都呈扁长的环形,表现出单晶塑性各向异性性质;本质上,初始屈服面的形状变化是由细观变形机制的启动情况决定的;镁合金单晶应变硬化具有明显的运动硬化特征.

英文摘要：

For investigation of the plastic flow law of single crystal Mg alloy, the constitutive relation of Mg alloy is established with the crystal plasticity theory based on the mechanism of slip and twinning deformation. The numerical simulation for the initial yield surface of single crystal AZ31 are carried out by using the finite element method （FEM）. That is, the initial yield surfaces are predicted in offset 2×10^-4 and 5×10^-4 under three types of biaxial loading, respectively. By comparing the simulation results with the experimental data, it can be concluded that （1） the initial yield surfaces in offset 2×10^-4 and 5×10^-4 all present the flat ring, which indicates the anisotropic characteristic of crystal plasticity; （2） in essence, the variation of initial yield surfaces depend on the activity of meso deformation mechanism; （3） the strain hardening of single crystal Mg alloy show the obvious characteristic of kinematic hardening.