Study on cyclic deformation behavior of extruded Mg–3Al–1Zn alloy

Fatigue properties and cyclic deformation behavior of an extruded Mg–3Al–1Zn (AZ31) alloy were investigated by performing the strain-controlled low-cycle fatigue tests at room temperature. We believed that the total strain amplitude should be closely related to fatigue properties and cyclic damage process. This study aimed to investigate the deformation mechanism from the viewpoint of strain amplitude. We found that when the total strain amplitude increased from 0.3% to 0.4%, there was a noticeable change in compressive peak stress amplitude, which might correspond to the competition between twinning–detwinning process and dislocation slips. Microstructure and fracture morphology were investigated using optical microscopy and scanning electron micrograph. At the total strain of great amplitude, fracture surfaces were characterized by the striation-like features and dimple-like structures.

► The fatigue deformation mechanism of the extruded AZ31 Mg alloy was investigated. ► Detectable difference was found between the strain amplitudes of 0.3% and 0.4%. ► 20 cycles may be a threshold value of cyclic compressive hardening.