Effective strategies for improving the mechanical stability of aged Mg-Li alloys

[Display omitted] •Designed a new Mg-Li alloy with exceptional mechanical stability post-aging.•Showed that the solid solution of Ag in the β-Li phase improves alloy stability and slows Li atom diffusion during aging.•Highlighted the inhibition of the transition from MgLi2Zn (strengthened phase) to MgLiZn (softened phase) by Ag atoms.•Provided Experimental and theoretical insights into addressing the age-softening issue in Mg-Li alloys. To date, the aging softening of Mg-Li-Zn based alloys has been a critical issue limiting their industrial application. Here, we design a new Mg-Li alloy that exhibits exceptional mechanical stability after solution treatment and then water quenching by means of a hitherto unrecognized mechanism. The results indicate that precipitation of a semi-coherent MgLi2(ZnAg) phase leads to rapid age-hardening of the Mg-Li alloy after water quenching, as evidenced by the Ag atoms in the precipitate. A massive solid solution of Ag atoms in the β-Li phase strengthens the stability of the alloy and retards the diffusion of Li atoms from the β phase into the α matrix during aging. Zn atoms in the MgLi2Zn precipitate are replaced by Ag atoms which explain the origin of age-hardening and inhibit the evolution of the substable strengthened phase MgLi2Zn to the equilibrium softened phase MgLiZn. This research may contribute to the theoretical basis for solving the age-softening problem of Mg-Li alloys.