Volume Effects in Bulk Metallic Glass Formation

Abstract

AbstractAtomic volume effects in amorphous alloys obtained by rapid solidification and in bulk glasses are briefly reviewed. It is recalled that at high undercoolings, the release at the growth fronts, of the volume corresponding to the reduction of the molar volume upon solidification can sharply accelerate crystal growth in the melt through viscosity reduction. A method is then proposed for estimating the volume of mixing ΔVmix which is negative for elemental additions to glass-forming liquid alloy. It is argued that negative ΔVmix reduces atomic mobility in easy glass-forming alloys thus allowing the suppression during cooling, of nucleation and growth of crystallites. The ZrCuNi system is used as an example for applying this reasoning. It is shown that Al or Ti addition to ZrNiCu alloys lead to strongly negative ΔVmix and expected sharp drops in diffusion-controlled crystal growth kinetics in the melt.