不同取样方向AZ31B镁合金应变率效应

Research on Strain Rate Effects of AZ31B Magnesium Alloy of Different Orientation Samples

采用分离式Hopkinson压杆获得了冲击压缩方向与热轧态AZ31B镁合金板材法向分别成90°、45°及0°的动态应力—应变曲线,利用光学显微镜及透射电子显微镜对微观组织演化过程进行了分析。结果表明:应变率约为1 200 s-1,压缩方向与板面法向成90°时,孪晶的面积分数随应变量的增大逐渐增加,孪生是主要变形机制,其曲线为凹型;压缩方向与板面法向成45°及0°时,其塑性变形以位错滑移为主,曲线形状分别为近似线型和凸型;应变率约为2 800 s-1,压缩方向与板面法向成90°时,孪晶面积分数迅速增加,大多数晶粒取向发生了改变,有利于滑移,其曲线由较低应变率的凹形变为凸型。

Dynamic mechanical properties of the samples with compression axis 90°, 45°or 0° from the normal direction of the AZ31B plate were tested using split Hopkinson bar. The microstructure evolutions were analyzed using optical microscope and transmission electron microscope. The analyzed results indicate that the twinned area fraction increases gradually with the increment of the strain, the twinning is main deformation mechanism, its stress-strain curve is concave, for the sample with 90° angle between compression axis and normal direction at a strain rate 1200 s^-1 ; the main plastic deformations are dislocation and slip, their stress-strain curves are approximate line and convex respectively, for the samples with the angles of 45°, 0° between compression axis and normal direction at a strain rate of 1 200 s^-1 ; the curves .change from concave to convex for 90° sample at a strain rate of 2 800 s^-1 , due to rapidly increasing twinned area fraction, which changes the orientations of most grains and makes slipping more easily.