Effect of electropulsing on edge stretchability and corrosion resistance near the punched edge of a 2024T4 aluminum alloy sheet

The punched aluminum alloy components possess limited edge stretchability for subsequent edge stretching deformation and poor corrosion resistance in their service periods due to the punched edges' complexity and heterogeneity, while electropulsing has a positive effect on the influencing factors which are closely interrelated with the above-mentioned two issues. Therefore, this paper focuses on the influence of electropulsing on the edge stretchability of punched holes obtained by electropulsing assisted punching (EAP) and the corrosion susceptibility of punched parts after electropulsing treatment. The hole expansion tests and immersion corrosion experiments were firstly carried out and analyzed. Furthermore, metallographic microstructure and scanning morphology of the healed of microcracks near the punched edge were observed by optical microscope and scanning electron microscopy (SEM) respectively. The experimental results demonstrate that the improvement of the edge stretchability depends on the patterns of applying electropulsing and electric current density (ECD). Moreover, the corrosion resistance of the punched parts after electropulsing treatment is enhanced, and the degree of improvement of corrosion resistance is more remarkable with the increase of the ECD. Comprehensive analysis reveals that the improvement of the punched parts' performance may be attributed to the healing and arrest of microcracks and microvoids near punched edge, local refinement of microstructure near the punched edge and the reduction of strengthening phases under the action of electropulsing, besides the promotion of macroscopic quality of sheared surface, the partial elimination of edge strain hardening (ESH) and pre-damage in vicinity of punched edge.