Comparative effects of electrical pulse and conventional annealing on AZ91D magnesium alloy

Magnesium alloys have emerged as a crucial alternative material for lightweight structural components in aerospace, 3C electronics, and automotive manufacturing due to their low density and superior die-casting performance. However, AZ91D magnesium alloy exhibits anisotropy after rolling and needs to be improved by long-term annealing treatment, which reduces production efficiency and increases cost. In recent years, pulse current treatment has been widely used in material modification due to its efficient and environmentally friendly characteristics. This paper studied the effects of electric pulse annealing treatment and conventional annealing treatment on the microstructure and mechanical properties of AZ91D magnesium alloy. The effects of pulse current treatment on the material’s properties, texture, and microstructure after rolling were analyzed. The mechanism of pulse current non-thermal effect on grain boundary migration and second phase dissolution was expounded. The results show that pulse current annealing can be completed quickly at a lower temperature, and the tensile strength and elongation of the samples after this treatment are higher than those after conventional annealing. Specifically, it has been determined that 123 A/mm2 is the optimal parameter for pulse current annealing: compared with the samples subjected to conventional annealing, the grain size of the samples treated under this parameter is refined to 65.37 μm, with the tensile strength increased by 32.70% and the elongation increased by 20.65%. Additionally, 128 A/mm2 and 10 min are confirmed as the optimal parameters for post-rolling pulse current annealing; after annealing under these parameters, the tensile strength of the sample reaches 224.6 MPa, and the elongation reaches 7.4%. Furthermore, with the increase in pulse current annealing time, the number density of the second phase decreases, the peak of the basal texture deflects toward the non-basal plane, and the recrystallization rate increases. These experiments show that pulsed current annealing technology provides a new, efficient, green production solution. It is expected to promote its wide application in more fields.