Enhanced low-cycle fatigue life of an extruded AZ31B alloy after pre-ratcheting deformation

In this study, an extruded AZ31B alloys was processed with pre-ratcheting deformation following by fully reversed strain-controlled low-cycle test. The post low-cycle stress-strain response and fatigue life were investigated. It shows that the mean stress decreases with the decreasing of applied ratcheting cyclic valley stress and a negative mean stress always exists in these pre-ratcheting samples during the post cyclic test. The low-cycle fatigue life improves with the decreases of pre-ratcheting cyclic valley loading to −160 MPa and then rapidly declines. Based on the observation of microstructural evolution during pre-ratcheting process and low-cycle tests, the relationship between microstructure and life was discussed. {10–12} twinning–detwinning and Bauschinger effect of dislocation slipping was regarded to be responsible for the enhanced fatigue life.