利用Hopkinson压杆对Mg-3Li和Mg-3Li-1Sc合金进行了高应变率冲击实验,分析了添加少量Sc对Mg-3Li合金冲击变形行为及其应变率效应的影响.结果表明,在1350s～3000s-1应变率范围内,两种合金的动态应力-应变行为均表现出显著的应变率强化效应.但随应变率继续升高,合金的动态变形行为转为应变率弱化效应.在1350～3500s-1应变率下,Mg-3Li-1Sc合金比Mg-3Li合金的动态屈服强度显著提高.在高应变率冲击条件下,晶内滑移和孪生产生的加工硬化及微裂纹的产生、扩展致使二种合金的动态变形行为先呈现应变率强化效应而后呈现为应变率弱化效应.添加少量Sc后Mg-3Li合金显微组织的细化和细小弥散MgSc相的形成,是显著提高Mg-3Li-1Sc合金冲击变形抗力的主要原因.%The impact experiment for Mg-3Li and M g-3 Li-1 Sc alloys was conducted using the Split Hopkinson Pressure Bar (SHPB) at high strain rates. The effect of minor Scandium on the impact deformation behavior and strain rate effects of Mg-3Li alloy were aralyzed. The results show that the dynamic stress-strain behaviors of both alloys exhibit evident positive strain rate effect at strain rates from 1350s-1to 3000s-1. However, the dynamic deformation behaviors of both alloys change to negative strain rate effect with the increasing strain rate. At strain rates from 1350s-1 to 3500s -1 , the dynamic yield strength of Mg-3Li-1Sc alloy is enhanced significantly compared to that of Mg-3Li alloy. Under high strain rate impact loading, the strain-hardening generated by slip and twining inside grains causes the positive strain rate effect of deformation behaviors in two alloys, while the following negative strain rate effect is attribute to the initiation and propagation of micro-crack. The notable improvement of impact deformation resistance of Mg-3Li-1Sc alloy is mainly attributed to the grain refinement and the formation of small and uniformly distributed MgSc phase because minor Scandium addition.
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