Study on plasticity evolution of AZ31 magnesium alloy based on pre-twinned by angular rolling

To overcome the poor formability of wrought magnesium alloys caused by their limited plasticity and deformation modes, this study developed an optimized processing strategy to introduce tensile twins (TTWs) for enhancing secondary formability. AZ31 magnesium alloy sheets were rolled at 200 °C with a reduction rate of 9% at various angles relative to the rolling direction (RD): 0°, 30°, 60°, and 90°. The analysis of microstructure, texture and mechanical properties showed that the volume fraction of TTWs was up to 23.4 % in 30RD sample, which was 57.4%, 128.4%, and 167.8% higher than those of the 0RD (14.8%), 60RD (10.2%), and 90RD (8.7%) samples, respectively. Meanwhile, the 30RD sample exhibited the weakest basal texture with a texture intensity of 10.90, which was 9.8 %, 13.8 % and 31.3 % lower than the 0RD (12.09), 60RD (12.64) and 90RD (15.87) samples respectively, and 16.7 % lower than the initial sheet (13.09). This controlled weakening of the texture resulted in a fracture elongation as high as 23.29% in the 30RD sample, which represents a significant improvement of 33.2% compared to the initial sheet (17.48%), and is 2.9%, 64.6%, and 62.5% higher than those of the 0RD (22.63%), 60RD (14.15%), and 90RD (14.33%) samples, respectively. The high density of TTWs in the 30RD sample effectively randomized grain orientation and promoted the activation of non-basal slip systems, which was further supported by higher Schmid factor values. These changes enhanced the activity of non-basal slips during subsequent deformation, thereby contributing to an improved strength-plasticity synergy.