Fatigue damage development in extruded Mg-3Al-Zn magnesium alloy

Fatigue crack initiation and early crack growth of an extruded Mg-3Al-Zn (AZ31B) magnesium alloy were experimentally investigated by conducting fully reversed strain-controlled tension-compression fatigue experiments at two strain amplitudes of 1% and 0.3%. At a strain amplitude of 1%, two types of twin-induced microcracks were observed. Less fatigue damage can be caused by the twin-induced cracks than from slip-induced cracks. At a strain amplitude of 0.3%, slip-induced microcracks initiated from 30% to 80% of the fatigue life, and then propagated until the final failure. No twin-induced cracks were detected at 0.3% strain amplitude.