Making selective-laser-melted high-strength Al–Mg–Sc–Zr alloy tough via ultrafine and heterogeneous microstructure

For most safety-critical applications, the achievement of both high strength and high toughness is one of the key requirements for structural materials. However, strength and toughness are generally mutually exclusive. Here, we report a selective-laser-melted Al–Mg–Sc–Zr alloy with a good combination of strength and toughness, which is comparable to those of 7075-T651 high-strength wrought Al alloy. Despite the brittle crack associated with order-induced planar slip due to secondary Al₃(Sc,Zr) nano-precipitates, the fracture toughness was effectively improved via diverse intrinsic/extrinsic toughening mechanisms associated with its ultrafine and heterogeneous microstructure. The present work provides a potent strategy for fabricating high-strength and high-toughness Al-based alloys.