Crystal Nucleation in Supercooled Liquid Metals

Abstract

It is becoming increasingly clear that nucleation processes in liquids and glasses are more complicated than previously thought, often coupling to other phase transitions and ordering processes. Experimental and theoretical studies show the development of icosahedral short-range order in many supercooled transition metal and alloy liquids, which in some cases extends beyond nearest neighbor distances. This atomic and chemical ordering couples to the nucleation barrier, and may play a role in glass formation in some cases. Select experimental results are presented to demonstrate these points. These are discussed in light of nucleation theories, including the commonly used Classical Theory of Nucleation, diffuse interface theories, and coupled-flux theory, which takes account of the interaction between interfacial processes at the surface of the crystal nuclei and long-range diffusion fluxes.