Enhanced ductility of AZ31B magnesium alloy through a combined pre-stretching and electromagnetically induced electric pulse treatment process

Magnesium (Mg) alloys are widely used in industries such as aerospace, automotive, and electronics due to their low density and high specific strength properties. However, their limited plasticity and low elongation at room temperature during plastic deformation significantly restrict their applicability in manufacturing complex-shaped components. This study combines pre-stretching and induced electric pulse treatment (IEPT) processes to enhance the mechanical properties of AZ31B magnesium alloy, and microstructural evolution is systematically investigated. Experimental results indicate that this process significantly enhances the uniform elongation, while the yield strength shows no significant reduction compared to the as-received sample. The elongation initially increases and subsequently decreases with increasing voltage and pre-stretching levels. Optimal performance is achieved at a voltage of 6 kV and a pre-stretching strain level of 8 %, resulting in a uniform elongation of 43 %, which is 160 % higher than that of the untreated alloy. IEPT exhibits a pronounced softening effect, effectively suppressing work hardening. The competitive interaction between softening and hardening mechanisms causes the yield strength to initially increase and then decrease. Transmission Electron Microscopy (TEM) analysis reveals that 6 kV IEPT process promotes dislocation slip and accumulation at grain boundaries, forming dense dislocation walls that contribute to enhanced strain hardening. Repeated IEPT treatments accelerate dislocation motion and annihilation, promoting dynamic recovery and recrystallization, thereby significantly reducing the dislocation density. Electron Backscattered Diffraction (EBSD) analysis shows that IEPT leads to grain growth, suppresses the formation of {10–12} tensile twins, and activates non-basal slip systems, weakening the basal texture. These mechanisms collectively contribute to the remarkable improvement in the uniform elongation of AZ31B magnesium alloy. This study offers an advanced manufacturing processing, and new insights into enhancing the room-temperature plastic deformability of magnesium alloys.