Dual-scale dispersoid by Er/Zr microalloying for controlling microstructure evolution and strength-ductility synergy in Al–Mg alloys

Conventional Al-Mg alloys are difficult to optimize simultaneously in terms of strength, ductility, and corrosion resistance because they cannot be effectively strengthened by conventional heat treatment. In this study, a novel dual-scale dispersoid strategy was developed by combining Er/Zr microalloying with thermomechanical processing, resulting in the formation of nanoscale Al 3 (Er, Zr) particles and submicron Mn-rich Al 6 (Mn, Fe) dispersoids in an Al-Mg alloy. The dual-scale dispersoids refined the as-cast grain structure and exerted effective Zener pinning during rolling and annealing, thereby suppressing recovery and recrystallization, stabilizing the deformed substructure, and retaining a high dislocation density and abundant low-angle grain boundaries. Consequently, the modified alloy reached a tensile strength of 396 MPa after annealing at 275 °C, which is 17.5% higher than that of the base alloy. After annealing at 325 °C, it achieved a better strength–ductility balance, with a tensile strength of 345 MPa and an elongation of 22%, corresponding to a more than threefold increase in the strength-ductility product. Moreover, the dual-scale dispersoids optimized the precipitate distribution and enhanced corrosion resistance. This work provides a new dual-scale dispersoid design strategy for overcoming the strength-ductility-corrosion trade-off in non-heat-treatable Al-Mg alloys.