稀土镁合金长程应变速率下室温形变机制

Room temperature deformation mechanism of rare earth magnesium alloy under long-range strain rate

针对Mg-Y-Nd-Zr-Gd合金在室温条件下进行了常规应变速率(1×10^(-3)~1 s^(-1))以及超高应变速率(>1×10^(3) s^(-1))范围内的压缩形变测试,并对其力学响应以及微观组织演变进行了综合探究。结果显示,Mg-Y-Nd-Zr-Gd合金在两种应变速率范围内展现出迥异的形变特征。在常规应变速率范围内,不同应变速率下材料的力学性能特征相近,材料屈服之后加工硬化率持续下降。然而,当进入超高应变速率范围内时,材料的屈服点上升,并且加工硬化率出现平台并持续到材料断裂失效。常规应变速率下的主要形变机制为基面滑移以及拉伸孪晶,而超高应变速率下形变后出现大量的二次孪晶。通过IGMA分析发现,超高应变速率下等非基面滑移系被开动,高CRSS值滑移系的开动以及二次孪晶与复杂的非基面滑移的交互作用是Mg-Y-Nd-Zr-Gd合金超高应变速率下屈服点提升以及异常加工硬化的主要原因。

For Mg-Y-Nd-Zr-Gd alloy,a compression deformation test was conducted under conventional strain rate(1×10^(-3)-1 s^(-1))and ultrahigh strain rate(>1×10^(3) s^(-1))at room temperature,and its mechanical response and microstructure evolution were studied comprehensively.The results show that the deformation characteristics of Mg-Y-Nd-Zr-Gd alloy under two strain rate ranges are different.Within the conventional strain rate range,the mechanical properties of the material are similar under different strain rates,and the work hardening rate of the material continues to decrease after yielding.However,when entering the ultrahigh strain rate range,the yield point of the material rises,and the work hardening rate appears to plateau and continues until the material breaks.Under conventional strain rate conditions,the dominant deformation mechanisms are basal slip and tensile twins,while a large number of secondary twins appear after the ultrahigh strain rate deformation.According to IGMA analysis,it is found that the non-basal slip systems are activated at the ultrahigh strain rate.The activation of slip systems with high CRSS value and the interactions between secondary twins and complex non-basal slip are the main reasons for the yield point increase and abnormal work hardening of Mg-Y-Nd-Zr-Gd alloy at ultra high strain rate.