高应变速率下铸态AM80镁合金的变形行为及数值模拟

采用INSTRON准静态压缩实验机和分离式霍普金森压杆装置对铸造固溶态AM80镁合金不同应变速率下的压缩变形行为进行了研究，应变速率分别为0.0001s-1、800s-1、1050s-1、1600s-1、1850s-1和2100s-1。结果表明：当应变速率ε˙≤1850s-1时，实验用AM80镁合金的流变应力随应变速率的增大而增大，表现出明显的正应变速率敏感性；当应变速率增至2100s-1时，由于局部温升效应，合金产生了明显的动态软化，导致流变应力反而略有减小。采用Johnson-Cook材料模型对实验用AM80镁合金在不同应变速率下的变形行为进行描述，并取材料应变速率强化参数为应变速率的函数。对比结果表明，所建立的本构方程与实验结果基本吻合。此外，由于力学本构忽略了由形变引起的温升软化，基于ABAQUS的仿真结果在较低应变速率（800s-1）和高应变速率（1850s-1）的中低应变下与实验结果吻合得较好;而在高应变速率（1850s-1）的较高应变条件下,仿真结果与实验结果差异较大。

Deformation Behavior and Numerical Simulation of a Casting AM80 Magnesium Alloy under High Strain Rate Loading

The compression deformation behaviors of a solution treated AM80 magnesium alloy were investigated with strain rates of 0.0001s-1, 800s-1, 1050s-1, 1600s-1, 1850s-1 and 2100s-1 respectively using a INSTRON universal compression machine and a split Hopkinson pressure bar(SHPB) apparatus. The results show that the flow stress of the studied AM80 magnesium alloy increase with increasing strain rate as strain rate ε˙≤ 1850s-1, demonstrating a visible positive strain rate sensitivity. However, the flow stress decreases slightly as strain rate reaches to 2100s-1, which is attributed to the effects of local temperature rise promoting the dislocation slip and finally the flow stress decreases slightly. The Johnson-Cook model was employed in characterizing the effects of strain rate on mechanical behaviors of the alloy and the material strain rate hardening parameters were taken as a function of strain rates. The results show that the constitutive equation is in good agreement with the experimental ones. Furthermore, the neglects of local temperature rises under high strain rate loading, lead a good agreement to the experimental results at low and medium strains, and a obviously differences will be appeared at high strains for the numerical simulation flow stresses by using ABAQUS software.