Low-cycle fatigue characteristics of rolled Mg-3Al-1Zn alloy

Fatigue characteristics of rolled Mg-3Al-1Zn (AZ31) alloy were investigated by performing the low-cycle fatigue test along the rolling direction. The alloy was found to have a strong basal texture so that the fatigue deformation was predominated by the alternation of twinning and detwinning during each cycle, and this made the cyclic stress response unstable and introduced a non-zero mean stress and/or strain depending on the loading condition. An energy-based concept was successfully used to predict the low-cycle fatigue life because a plastic strain energy density was found to have good characteristics as a fatigue parameter; it was stabilized at the early stage of fatigue life and nearly invariant through entire life. In the life prediction model, the effect of mean stress was appropriately considered.