Defect-solute cooperativity mediated evolution of microstructure and mechanical properties in pre-deformed lean Mg alloys during aging

To elucidate the unresolved dynamic evolution of metastable bake-hardening during prolonged isothermal aging, the time-dependent microstructural evolution in 2 % pre-strained Mg-0.6Al-0.7Ce-0.4Ca-0.4Mn alloy under extended aging conditions was systematically investigated. Dislocation networks act as acceleration diffusion pathways facilitating solute redistribution. Furthermore, the co-segregation of Ca and Al atoms induces heterogeneous nucleation of thermodynamically stable nano-(Mg, Al)₂Ca precipitates during prolonged aging. This unique precipitation mechanism effectively compensates for the conventional weakening of dislocation pinning by solutes observed during thermal exposure. Residual matrix solutes progressively form high-density Guinier-Preston (G.P.) zones, which subsequently transform into nano-Al₂Ca precipitates while maintaining spatial distribution density. This work fundamentally uncovers a previously unrecognized age-hardening paradigm mediated by defect-solute cooperativity, providing critical insights for developing cost-effective Mg alloys with enhanced thermal stability.