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.