Roles of deformation twinning and dislocation slip in the fatigue failure mechanism of AZ31 Mg alloys

Fatigue tests were performed on AZ31 Mg alloys at room temperature in tension cycles. Deformation twinning of the {101¯2} type was observed both below and above the fatigue limit, indicating that the {101¯2} twins do not contribute directly to fatigue failure. However, prismatic slip and substantial cyclic hardening were observed above the fatigue limit. Progressive hardening gave rise to {1011}–{101¯2} double twinning that led to the formation of large surface steps, cracks and eventual failure.