高周疲劳试验中AZ31镁合金组织和性能的演变特征（英文）

Evolution characteristics of microstructure and properties in AZ31 alloy during high cycle fatigue processes

利用扫描电镜和电子背散射衍射技术研究AZ31镁合金在高周疲劳试验中不同循环周次(包括10~4(样品1)、10~6(样品2)和无(样品3无疲劳试验))条件下的组织和性能的演变规律。结果表明,经拉压循环变形后,产生了大量{1012}拉伸孪晶,还产生了少量的{1011}拉伸孪晶和{1011}-{1012}二次孪晶。样品1,2和3中{1012}拉伸孪晶的体积分数分别为8%、21%和4%。疲劳断口分析发现大面积疲劳辉纹和理解断裂的区域,韧窝直径大小随着加载次数的增加而增大。孪晶片层容易产生于裂纹萌生区,韧窝则在终断区产生。样品1、2和3的韧窝尺寸分别为14.8、31.2和8.5μm。样品的疲劳强度和伸长率随着加载次数增加稍有降低。

In order to investigate the microstructure and properties evolution of the AZ31magnesium alloy in different cycles(including104(sample1),106(sample2)and none(sample3,no fatigue tests on the samples))of high cycle deformation,thescanning electron microscopy(SEM)and electron back-scattered diffraction technique(EBSD)were fully used.It is found that many{1012}tension twins(near21%,volume fraction),a few{1011}compression twins and{1011}?{1012}secondary twins aregenerated during tension?compression cyclic deformation.The volume fractions of{1012}twins in samples1,2and3are8%,21%and4%,respectively.By analyzing the fatigue fracture of the samples,larger area of fatigue striations and cleavage fracture insamples are also observed,as well as the shallower dimples.The twin laminae are likely to occur in the crack initiation zone whiledimples are in the final fracture region and the dimple size increases with the increase of the cycle number.The dimple diameters ofsamples1,2and3are14.8,31.2and8.5μm,respectively.It turns out that both the fatigue strength and elongation of the samplesslightly decrease with increasing the cycle number.