High cycle fatigue behavior of extruded and double-aged Mg-6Zn-1Mn alloy

Abstract High cycle fatigue behavior of extruded and double-aged Mg-6Zn-1Mn alloy was investigated by servo-hydraulic fatigue testing machine with pull-push sinusoidal loading. Results show that double-aged alloy shows a deteriorative fatigue performance despite having excellent tensile strength. Twinning and detwinning mechanisms play a dominate role in fatigue deformation process in double-aged alloy. However, for extruded alloy, duo to the duplex grain structure, the fatigue deformation mechanism presents various deformation modes: in high stress regime (≥129 MPa) twinning takes part in fatigue process and appears in coarse grains, in low stress regime (≤125 MPa) fatigue deformation was dominated by slip. Microstructures of post-fatigue specimens are remarkably refined, room temperature recrystallization during fatigue has also been found in Mg-6Zn-1Mn alloy.