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.