Formation Properties of Cluster Structures during the Rapid Solidification of Liquid Ca<sub>7</sub>Mg<sub>3</sub> Alloy

A molecular dynamics simulation was performed to examine the formation properties of clusters during the solidification of liquid Ca7Mg3 alloy. Pair distribution functions, Honeycutt-Andersen (HA) bond-type index method, cluster-type index method, and genetic tracking were used to analyze the formation and evolution of cluster structures during rapid solidification processes. Results show that amorphous structures are mainly formed with the 1551, 1541, and 1431 bond-types at a cooling rate of 1×1012 K·s-1. The basic cluster (12 0 12 0) plays a key role in the formation of amorphous structures during rapid solidification processes. The stability of a cluster is related to the type of basic clusters and also the type of central atoms as well as the bonding modes between all central atoms. Bonding among the basic clusters (12 0 12 0) allows the formation of larger clusters because of the lower energy and the better genetic characteristic of the basic cluster (12 0 12 0). These bigger clusters are obviously different from those obtained by gaseous deposition and ionic spray methods.