Simulation of formation and evolution of nano-clusters during rapid solidification of liquid Ca70Mg30 alloy

A molecular dynamics simulation study was performed to investigate the formation and evolution mechanisms of nano-clusters during the rapid solidification of liquid Ca70Mg30 alloy. The cluster-type index method (CTIM) was adopted to describe microstructure evolutions of nano-clusters during solidification. Results indicate that amorphous structure is mainly formed with three bond-types of 1551, 1541 and 1431 at the cooling rate of 5×1011 K/s, and glass transition temperature Tg is about 530 K; the icosahedron cluster of (12 0 12 0) plays a key role in formation of amorphous structure, and smaller Mg atoms are much more probable to be central atoms of icosahedron clusters; and nano-clusters are mainly formed by combining medium-size clusters. Interestingly, it was also found that formation and evolution processes of the nano-cluster display a three-stage feature which is analogous to crystallization process of amorphous alloy.