An EFTEM study of compositional variations in Mg–Ni–Nd bulk metallic glasses

A range of Mg–Ni–Nd bulk metallic glasses has been cast. Around the composition Mg65Ni20Nd15 (at.%), but not at neighbouring compositions, energy-filtered transmission electron microscopy provides evidence for strong compositional inhomogeneities in the as-cast glass. In this fully glassy material, an apparent two-phase cellular microstructure is seen; one phase is rich in Ni, the other in Mg and Nd. Annealing at a temperature just above the glass transition, or even holding at room temperature for several months can eliminate the inhomogeneities. The diffusivity values derived from the homogenization kinetics are in good agreement with those known for other bulk metallic glasses. The present results suggest the existence of a closed-loop miscibility gap in the glass-forming liquid.