AZ31B镁合金大应变循环变形行为研究

为了研究AZ31B镁合金在大应变幅条件下的变形机制,开展了该合金在7.嬲应变幅条件下的循环行为研究.结果表明:在拉伸阶段的最大应力值随着循环周次的增加而减小,而在压缩过程中的最大应力值随着循环周次的增加而增大,在整个循环过程中材料呈现循环应变硬化特性,拉应力是导致循环应变硬化的主要原因;随着循环周次增加,滞回曲线的不对称性基本不变.真应力-真应变滞回曲线在卸载和反向拉伸阶段出现3个拐点.在压缩过程中发生{10-12}孪生,反向拉伸过程发生去孪生行为,包申格效应对去孪生行为具有较大影响.研究表明:孪生-去孪生是大应变幅循环变形的主要变形机制;对拉伸、反向压缩过程的变形特征及机制的分析,可为低周疲劳行为的研究提供参考.

Cyclic deformation behavior of AZ31B magnesium alloy at large amplitude

In order to research the deformation mechanism of material under large amplitude conditions, the cyclic deformationbehavior of an extruded AZ31B magnesium alloy with the fiber texture components was investigated under tensile-tensile asymmetric strainloading at 7.5% amplitude. It was found that the maximum tensile stress decreased with the increase of cyclic number,while the maximumcompressive stress increased,the alloy presented cyclic strain-hardening characteristics in the whole cycle. The cyclic hardening wasresulted from tensile deformation; the asymmetry of the hysteresis loop basically unchanged during the whole cyclic. Three turning pointsappeared during unloading and reversal tension process on the true stress-true strain curves. {10-12} tension twinning was activated incompressive process and its detwinning happened in reversal tension process, Bauschinger effect has a greater impact on the detwinning. Itwas found from deformed microstructures that twinning-detwinning is dominant plastic deformation at the high amplitude.Through theanalysis of the deformation characteristics and mechanism of stress and reversal tension process, it can provide reference for the research oflow cycle fatigue behaviors.