Evading strength-corrosion tradeoff in laser-melted Al alloys through twin-related grain boundary engineering

Breaking the strength-corrosion tradeoff in fine-grained Al alloys remains elusive due to incompatible grain boundary requirements. We report laser-melting-induced hierarchical fine twin architecture where coherent twin boundaries (spacing ∼3 µm) simultaneously enhance hardness (14% higher) and corrosion resistance (85% lower corrosion depth). The twin boundaries containing stacking faults, unlike conventional high-angle grain boundaries, demonstrate remarkable stability against second-phase precipitation during prolonged thermal exposure. This work presents a new paradigm for laser additive manufacturing and laser welding of damage-tolerant alloys to implement twin-related grain boundary engineering, transcending traditional composition-dependent approaches.