AZ31 B镁合金在高周疲劳过程中的加工硬化/软化行为及温度变化

摘要

使用红外热像仪测试 AZ31B镁合金在疲劳和拉伸过程中的温度变化,并对疲劳后的AZ31B镁合金试样进行拉伸试验,研究了疲劳过程中该合金的加工硬化/软化行为.结果表明:当疲劳时的最大应力高于其疲劳强度时,AZ31B镁合金在疲劳过程中的温度变化可依次分为初始升温阶段、温度下降阶段、温度稳定阶段、快速升温阶段和断裂后自然降温阶段;随循环次数增加,试样交替发生加工硬化和软化,导致疲劳后试样的抗拉强度呈先增后降再增的变化趋势;由于疲劳时不同应力水平引起了不同程度的加工硬化,使得疲劳后试样的抗拉强度随疲劳时最大应力的增大而增大.%The temperature evolution of AZ31B magnesium alloy in fatigue and tensile processes was measured with infrared imager.The work-hardening/softening behavior of the alloy during fatigue process was studied by conducting tensile tests on the fatigued AZ31B magnesium alloy samples.The results show that the temperature evolution process of the AZ31B magnesium alloy during fatigue was divided into five stages including initial temperature rising,temperature falling,temperature stabilizing,rapid temperature rising and natural temperature falling after fracture in sequence when the maximum stress during fatigue was higher than the fatigue strength of the alloy.The tensile strength of the fatigued sample increased and then decreased and then increased with the number of cycles increasing,due to the fact that the work-hardening and softening occurred in turn of the samples.With the increase of the cyclic maximum stress,the tensile strength of the fatigued sample increased because of the different work-hardening levels caused with the different stress levels during fatigue.