AZ31B镁合金动态力学行为及变形机制

摘要

为了研究挤压态AZ31B镁合金在高应变速率下的力学行为及变形机制,采用分离式Hopkinson压杆和反射式拉杆装置在室温对挤压态AZ31B镁合金进行了动态压缩和拉伸试验,平均应变速率范围在500～2 600 s-1之间,用光学显微镜观察了测试后试样的微观组织变化.结果发现,由于在挤压过程中形成了基面织构,沿挤压方向压缩时,拉伸孪晶{1012}〈1120〉首先启动,屈服强度对应变速率不敏感,且屈服强度较低,但在塑性变形的第二阶段,位错滑移参与变形,应变速率硬化效应显著;沿挤压方向拉伸时,压缩孪晶{1011}〈1120〉和非基面滑移是其主要的塑性变形机制,合金屈服强度较高,并表现出轻微的正应变速率效应;由于织构的形成,合金在压缩和拉伸时表现出很强的拉压不对称性,压缩屈服强度与拉伸屈服强度的比值约为0.32.%In order to investigate the mechanical behavior and deformation mechanism of extruded AZ31B magnesium alloy at high strain rates,the dynamic compression and tension tests were carried out for extruded AZ31B magnesium alloy with the split Hopkinson pressure bar and reflect tension bar apparatus.The average strain rates were in the range from 500 s-1 to 2 600 s-1.The microstructural change of tested samples was observed with optical microscope.The results show that due to the formation of basal plane texture in the extrusion process,the tension twins {1012}1120 are firstly activated when the sample is compressed along the extrusion direction.The yield strength is insensitive to strain rate,and is lower.But at the second stage of plastic deformation,the dislocation slips take part in the deformation,and the strain rate hardening effect is notable.When the sample is elongated along the extrusion direction,the compression twins {1011}1120 and non-basal plane slips are the main deformation mechanisms.In addition,the yield strength of the alloy is higher,and the alloy shows a slightly positive strain rate effect.Due to the formation of texture,the alloy shows the intense tension-compression asymmetry in the tension and compression processes,and the ratio between the compression and tension yield strengths is about 0.32.