应变速率对AZ31挤压变形镁合金力学行为的影响

Influence of strain-rate on mechanical behavior of as-extruded AZ31 magnesium alloy

通过静态拉伸试验机和高应变速率冲击拉伸试验装置,对AZ31挤压镁合金分别进行了不同应变率下拉伸力学性能的试验,获得了各应变速率下完整的应力-应变曲线。并通过扫描电镜对其拉伸断口进行分析。结果表明,其屈服应力、拉伸强度随着应变速率的增加而增加,失稳应变则随着应变速率的增加而有所减小;而弹性模量则对应变率不敏感。采用Johnson-Cook材料模型描述AZ31镁合金应变速率相关的应力应变本构模型,其拟合结果和实验结果基本相吻合。扫描电镜断口分析结果表明,动态和静态的断裂方式基本相同,都是以准解理断裂特征为主,局部区域伴有解理断裂。

Tensile experiments were carried out for as-extruded AZ31 magnesium alloy under different strain-rates on a static tensile testing machine and tensile impact testing apparatus.Fracture morphology was analyzed by SEM.The results show that yield strength and ultimate tensile strength of the alloy increases with the increase of strain rate,and the failure strain decreases with increasing strain rate,however,no significant effect of strain rate on Young’s modulus E is observed.The Johnson-Cook model is employed in characterizing the effect of strain rate on mechanical behavior of the alloy and the calculated result is accordant well with the experimental results.SEM fractographic analysis indicates that a mixed mode of predominant quasi-cleavage fracture with local cleavage fracture presents for both static and impact loading.