An experimental study of anisotropic fatigue behavior of rolled ZK60 magnesium alloy

Abstract

The strong anisotropy of wrought magnesium alloy significantly affects its application in structural components bearing fatigue loads. This study aims to explore the effects of grain orientations (RN-N versus RN-R) and sampling surfaces (RT-R versus RN-R) on the fatigue behavior of the ZK60 Mg alloy. Stress-controlled fatigue tests and quasi-in-situ EBSD tests were carried out on three different specimens. The sampling surface and grain orientation both have significant effects on the fatigue life of samples, especially at low-stress amplitude. Although the sampling methods are different, the three samples show similar cyclic evolution patterns. The consumption of available twins dominates the cyclic hardening behavior in the fatigue early stage. When loaded along ND, abundant intersecting twins induced by various variants can produce large plastic deformation, which is detrimental to the fatigue resistance of RN-N samples. When loaded along RD, the activation of specific twin variants leads to the reduction of the twinning areas, thus decreasing the plastic deformation of RN-R and RT-R samples. In addition, the constraint force along the width direction and sandwich-like metallographic structure of RN-R samples will hinder the activation and growth of twins, which results in smaller twinning areas and higher fatigue life than RT-R samples.