Mg-Gd-Y与AZ31两种变形镁合金的冲击波响应

Shock-Loading Response of Mg-Gd-Y and AZ31 Wrought Magnesium Alloys

利用平行平面正碰撞方法产生的冲击波对Mg-Gd-Y与AZ31两种典型变形镁合金加载,并对回收后的材料进行准静态压缩实验,采用金相显微镜和透射电子显微镜进行微观组织分析。冲击波加载后,原始固溶态Mg-Gd-Y合金的屈服强度增加了21 MPa,而时效峰状态合金的屈服强度仅增加4 MPa,时效处理后产生的析出相β'使合金的屈服强度增加幅度明显减少;然而,AZ31镁合金的屈服强度增加了40 MPa。Mg-Gd-Y与AZ31镁合金的冲击波加载后力学响应的差异取决于冲击波过程中两者所具有的不同变形机制,冲击波变形后Mg-Gd-Y合金中的孪晶体积分数非常少,其变形机制以位错滑移为主。相比之下,冲击波加载后的AZ31合金中产生了大量孪晶,孪生是该合金的一种重要变形机制。孪晶界在后续再加载过程中成为位错滑移的障碍,从而导致AZ31镁合金表现出更为显著的冲击波强化效果。

The Mg-Gd-Y and AZ31 magnesium alloys were subjected to shock wave loading by using the plain symmetry impact experiment.Then,the uniaxial compression tests were carried out on the recovered shock-deformed samples.Optical microscopy（OM） and transmission electron microscopy（TEM） were used to observe the microstructure.The increased magnitude of the yield strength of the samples for the solutionized and peak-aged Mg-Gd-Y alloy was 21 MPa and 4 MPa,respectively.Therefore,the precipitate phase β′ in the peak-aged condition was responsible for the decreased shock strengthening.In contrast,the AZ31 alloy showed a more notable shock-strengthening.The difference of the mechanical behavior between Mg-Gd-Y and AZ31 under shock wave loading was dependent on the discrepancy of deformation mechanisms.The twinning volume fraction for the shock-deformed Mg-Gd-Y alloy was low,indicating that the dominant deformation mechanism was dislocation slip.Whereas,there existed plenty of twinning in the shock deformed AZ31 alloy.The notable shock-strengthening was attributed to the twinning boundary being the obstacles of the dislocation glide in the post-shock reload process.