Defect healing enabled superb cold rollability of Mg alloys by electropulsing

• Electropulsing enables ultrafast defect healing in Mg alloys within seconds. • Local thermal compressive stress dominates rapid defect closure under high current density. • Multi-physics simulation reveals current–density-dependent defect healing mechanisms. • Enhanced ductility and superb cold rollability are achieved in Mg alloy thin strips. Magnesium (Mg) alloys face severe edge cracking during cold rolling due to limited slip systems and deformation anisotropy. Conventional hot rolling and heat treatment compromise efficiency and surface quality when fabricating Mg alloy thin strip. Here, we pioneered an electropulsing treatment (EPT) strategy to simultaneously heal internal defects and restore rollability in multi-pass cold rolling of Mg-1Zn-1Gd alloy. Through microstructure/defect characterizations and multi-physics simulations, we revealed that the local thermal compressive stress, induced by inhomogeneous Joule heating near defects, dominated defect healing within seconds; while a concomitant slower healing process was driven by the global compressive stress and accelerated atomic diffusion, which could result in excessive grain growth with prolonged EPT. Optimized EPT parameters achieved a balance between internal defect and microstructure, i.e. one-order reduction in defect volume fraction and a partial recrystallization state with relieved residual stress, and endowed the annealed sample with significantly enhanced ductility and superb cold rollability. Overall, this study established a scalable and efficient route for Mg alloy thin strip fabrication.