Improvement of strength-ductility synergy of Mg–Al–Mn alloy using laser shock peening-induced gradient nanostructure

The trade-off between strength and ductility of magnesium alloy is a general bottleneck. Herein, we presented a method, laser shock peening (LSP), to overcome this problem. The key is the preparation of plastic strain-induced gradient nanostructure along the depth direction. Gradient nanostructure has unique deformation mechanism in the process of tensile deformation. Due to the cooperative effects of deformation twinning, dislocation movement, and dynamic recrystallization, the gradient nanostructured AM50 magnesium alloy contributed to ∼12% improvement of ultimate tensile strength, while ∼3% reduction of tensile ductility. Furthermore, the formation mechanisms of LSP-induced gradient nanostructure at initial plastic deformation stage, severe plastic deformation stage, and surface nanocrystalline stage were explored.