The role of twinning–detwinning on fatigue fracture morphology of Mg–3%Al–1%Zn alloy

Typical fracture morphology of Mg–3%Al–1%Zn (AZ31) alloy after low cycle fatigue was investigated using SEM and optical microscope. It is shown that prolific lamellar structure in the crack initiation and crack stable propagation zone mainly results from twinning, while dimple structure formed in the unstable crack propagation and final rupture zone is mainly due to slip. The formation mechanisms of corresponding morphologies are proposed based on twinning and detwinning processes during compressive and tensile loading half cycles, respectively, for this alloy.