多向高速冲击下LZ91镁合金的力学性能及组织

Mechanical Properties and Microstructure of LZ91 Magnesium Alloy under Multidirectional High Speed Impact

常温下采用霍普金森压杆在冲击气压为0.2MPa~0.7MPa的条件下对LZ91镁合金进行多向高速冲击,结合变形后的微观组织及应力应变曲线,分析应变速率和不同冲击方向对微观组织演变的影响。结果表明,冲击过程中β-Li和α-Mg的滑板效应和形变温升产生的软化作用和加工硬化存在竞争关系,导致随着应变速率增加和材料初始组织中位错密度的增加,应力应变曲线并不呈现单调增加的趋势;当局部应力达到一定程度,就会在材料内部产生绝热剪切带,继而在绝热剪切带内产生位错缠结并形成微型孔洞,最后形成裂纹。

In this paper,LZ91 magnesium alloy is subjected to multi-directional high-speed impact at room temperature with a Hopkinson bar at 0.2MPa~0.7MPa.Combined with the microstructure and stress-strain curve after deformation,the influence of strain rate and impact direction on microstructure evolution is analyzed.The results show that there is a competitive relationship between the sliding plate effect ofβ-Li andα-Mg,the softening effect and work hardening caused by deformation temperature rise.The stress-strain curve does not increase monotonically with the increase of strain rate and dislocation density in the initial microstructure.When the local stress reaches a certain degree,adiabatic shear bands will be generated,and then dislocation tangles and micro holes will form in the adiabatic shear band,and finally leading to the initiation of cracks.