Formation and evolution of nano-clusters in a large-scale system of Cu–Zr alloy during rapid solidification process

Abstract

To investigate the formation and evolution mechanisms of nano-clusters formed during the rapid solidification process, a molecular dynamics (MD) simulation study has been performed for a system consisting of 106atoms of Cu64.5Zr35.5 alloy. Adopting a new cluster-type index method (CTIM-3) to analyse the local atomic clusters, it is found that the dominant microstructural configurations in the supercooled liquid and amorphous are the icosahedrons and their combinations, especially the intercross-sharing (IS) clusters linked of two icosahedrons (IS-ICO-clusters) can be used to build some larger IS-ICO nano-clusters with different sizes. Highly interesting, in the system the number of atoms in various IS-ICO nano-clusters demonstrates a magic number sequence of 19, 23, 25, 27, 29, 31, 33, 35, 37, 41, 43, and so on. The magic number clusters can be classified into three main types: chain-like, triangle-tailed and quadrilateral-tailed. The degree of tightness for IS-ICO nano-cluster can be expressed by formula nI/nIS. And some IS-ICO nano-structures have stronger mechanical stability and can bear higher load.