Low-cycle fatigue behavior of solutionized and aged WE43 magnesium alloys at room temperature

The low-cycle fatigue behavior of solutionized (T4) and aged (T6) WE43 magnesium alloys was studied at room temperature. The total strain amplitudes (Δε_t/2) were 0.4%, 0.5%, 0.6%, 0.7% and 1.0%. Detailed microstructure evolution was characterized by scanning electron microscope (SEM), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). The results showed that plastic strain amplitude decreased with the increasing cycle number in T4 alloy, which is due to the dense persistent slip bands (PSBs) and dynamic precipitates hindering <a> dislocation slip. In contrast, the plastic strain amplitude increases gradually in T6 alloy, which is attributed to the enhanced activation of pyramidal slip. The low-cycle fatigue life of T6 alloy with larger fatigue ductility coefficient is longer than that of T4 alloy. The Coffin-Manson model can accurately predict the fatigue life of T4 and T6 alloys compared to Jahed-Varvani (JV) energy model. For T4 alloy, the fatigue damage mechanism was dominated by basal slip. For T6 alloy, the enhanced pyramidal slip plays an important role to accommodate plastic deformation.