Cluster Evolution in Undercooled Melt and Solidification of Undercooled Ge-based Alloy Melts Induced by Extrinsic Clusters

The structure or short-range order of clusters in undercooled metallic melts is influenced, to some extent, by the interfacial free energy between the cluster and the melt. Analyses of the effects of interfacial energy on the cluster structure based on the Gibbs equation show a possibility that atoms in the clusters tend to be packed more loosely with the increasing cluster size (or the undercooling). Nucleation may occur, following these analyses, when clusters reach a definite size and atoms in the clusters relax to some extent to form the crystal structure. Indirect support to this viewpoint is provided by the present results of cluster-induced nucleation experiments on undercooled Ge_73.7Ni_26.3 alloy melts.