Activation Behavior of {10-12}-{10-12} Secondary Twins by Different Strain Variables and Different Loading Directions during Fatigue Deformation of AZ31 Magnesium Alloy

Abstract

The tensile and compression fatigue deformation tests of AZ31 magnesium alloy were carried out at room temperature, and the activation behavior of {10-12}-{10-12} secondary twins in different loading directions (ND normal direction, RD rolling direction) and different strain amplitude (0.5%, 1%) was studied. The results showed that {10-12}-{10-12} secondary twins were observed on the fracture surface of the fatigue samples in the ND at the strain of 1%. In contrast, no secondary twins were observed in the ND at the strain of 0.5% nor in the RD at the strain of 1% and 0.5%, and the fatigue life in the ND was greater than that in the RD. The analysis showed that the generation of {10-12}-{10-12} secondary twins was associated with the grain size and loading direction and that the fatigue deformation at 1% strain was more likely to generate {10-12}-{10-12} secondary twins due to the large lamellar thickness of the primary twins generated at relatively large strain conditions. The fatigue deformation along the ND tension was more favorable for the activation of multiple {10-12} primary twins, and the interaction of multiple twin variants was more favorable to activate {10-12}-{10-12} secondary twins.