Equilibrium and metastable phases in a designed precipitation hardenable Mg–3Gd–3Nd–0.6Zr alloy

A precipitation hardenable Mg–3Gd–3Nd–0.6Zr alloy was designed by thermodynamic calculations firstly and then investigated by experiment. In the as–cast alloy, the solution of Nd atoms into equilibrium Mg5Gd phase facilitated its formation and increased its lattice constant. After a two–step solution and a two–step aging treatment, the alloy showed remarkable age–hardening response, which was caused by the formation of massive fine β1 precipitates. It is quite possible that the β1 phase is a continuous solid solution with metastable Mg3Nd and Mg3Gd phases.