Effect of aging treatment on low-cycle fatigue behavior of extruded Mg–8Al–0.5Zn alloys

The low-cycle fatigue properties of Mg–8Al–0.5Zn (AZ80) magnesium alloy have been studied as a function of precipitation state. It has been shown that the presence of precipitates significantly reduces tension–compression yield asymmetry, compared with solution treated material. This decreased asymmetry significantly reduces tensile mean stress during low-cycle fatigue process. As the cyclic deformation progressed, an abrupt increase in the plastic strain amplitude prior to failure is observed, representing the onset of fatigue crack initiation. This increase disappears in the aged sample, which leads to the significantly decreased area of crack propagation zone, and shorter lifetime. Due to the enlarged reverse plastic zone size, the aged sample showed microscopically rough faceted fracture surfaces in the fatigue crack propagation zone.

► Tension–compression asymmetry was reduced by aging.
► The presence of precipitates reduces mean stress in fatigue.
► The plastic strain amplitude determines the fatigue lifetime.
► The difference in fractograph is due to reverse plastic zone size.