Effective strategies for improving the mechanical stability of aged 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.