In-situ study of mechanical response and microstructure evolution of AZ31B magnesium alloy after pre-tensile deformation treatment

To investigate the effect of pre-tensile deformation along the rolling direction on the quasi-static tensile properties of AZ31B magnesium alloy, different levels of pre-tensile deformation were applied to rolled AZ31B sheets. In-situ multi-scale experiments and molecular dynamics simulations were combined to clarify how pre-tensile deformation affects microstructural evolution, strengthening, and damage accumulation during subsequent loading. The results show that increasing pre-tensile deformation gradually improves tensile strength while reducing plasticity. Pre-tensile deformation promotes dislocation accumulation and changes the activation ability of slip systems during subsequent deformation. By combining infrared temperature evolution with stress-strain curves, the thermodynamic entropy flow during tensile deformation was calculated. This increasing entropy flow marks the transition from elastic deformation to stable, and ultimately unstable, plastic deformation. Meanwhile, pre-tensile deformation introduces irreversible damage and microscale defects at grain boundaries, reducing material stability. Under subsequent tensile loading, numerous stress concentration regions are formed, promoting crack propagation and causing some grains to fail prematurely without sufficient plastic deformation. This study reveals the competing effects of mechanical pre-tensile deformation on strengthening and damage accumulation in AZ31B magnesium alloy, providing a theoretical basis for developing high-performance magnesium alloys and optimizing their mechanical properties.