高应变速率下铸态AM80镁合金的变形行为及数值模拟

摘要

The compression deformation behaviors of a solution treated AM80 magnesium alloy were investigated with strain rates of 0.0001 s-1 ,800 s-1 ,1050 s-1 ,1600 s-1 ,1850 s-1 and 2100 s-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 in-crease with increasing strain rate as strain rateε˙≤ 1850 s-1 ,demonstrating a visible positive strain rate sensitivity.However,the flow stress decreases slightly as strain rate reaches to 2100 s-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 obvious-ly differences will be appeared at high strains for the numerical simulation flow stresses by using ABAQUS software.%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0.0001 s-1、800 s-1、1050 s-1、1600 s-1、1850 s-1和2100 s-1.结果表明:当应变速率ε˙≤1850 s-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2100 s-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(800 s-1)和高应变速率(1850 s-1)的中低应变下与实验结果吻合得较好;而在高应变速率(1850 s-1)的较高应变条件下,仿真结果与实验结果差异较大.