Effects of electromagnetically driven impact and induced electric pulse treatments on mechanical behavior and microstructural evolution of pre-deformed AZ31B magnesium alloy

This study systematically compares the effects of two external field loading pathways, electromagnetically driven impact treatment (EDIT) and induced electric pulse treatment (IEPT), under different discharge voltages on the mechanical properties, yield behavior, and microstructural evolution of pre-deformed AZ31B magnesium alloy. EDIT subjects the material to a high strain rate loading condition dominated by electromagnetic impact, which promotes dislocation pile-up, substructure formation, and detwinning, while still enabling moderate grain refinement and preserving a high dislocation density, leading to the development of a pronounced yield plateau and a significant increase in yield strength. At the discharge voltage of 7 kV, the EDIT condition enhances the yield strength σ 0.2 by approximately 58% relative to the as-received alloy, while retaining appreciable ductility. The overall mechanical performance is therefore enhanced primarily through strength improvement. In contrast, IEPT is governed mainly by induced electric current and associated Joule heating. The resulting high temperature recovery and recrystallization substantially reduce the dislocation density and cause grain coarsening. This transition converts discontinuous yielding to continuous yielding and almost eliminates the yield plateau. Fractographic analysis indicates that EDIT promotes early strain localization during tensile deformation, accompanied by fracture surfaces with shallow dimples and local quasi-cleavage features. IEPT effectively delays localization and produces deep and dense dimples, indicative of a more stable plastic deformation mode. Further analysis correlates the emergence and suppression of the yield plateau with dislocation evolution, and identifies IEPT induced high temperature recovery as a key factor responsible for plateau suppression. In addition, increasing discharge voltage during EDIT reduces the amount of {10-12} tensile twinning and increases the fraction of low-angle grain boundaries, suggesting that electromagnetic impact promotes detwinning related microstructural evolution. These findings contribute to a deeper understanding of how different electromagnetic loading pathways regulate yielding behavior and plasticity mechanisms in magnesium alloys.