Simulation study of effect of cooling rate on evolution of microstructures during solidification of liquid metal Cu

Abstract

A molecular dynamics simulation has been performed on the solidification process of liquid metal Cu by adopting the quantum Sutton-Chen many-body potentials at four different cooling rates. Through the pair distribution function，bond-type indices, coordination number, MSD, and visualized analysis, it is found that the cooling rate plays a critical role in the evolution of microstructures of liquid metal Cu. At the cooling rate of 1.0×014K/s, the amorphous structures will be formed in the system; at the cooling rate of 1.0×1013K/s, 1.0×1012K/s and 1.3×1011K/s, the mixed crystal structures of fcc and hcp formed mainly with 1421 bond-type will coexist in the system, and their corresponding crystallization temperatures are 373K, 773K, 873K, respectively. Namely, slower the cooling rate, higher the crystallization temperature, and higher the degree of crystallization; and slower the cooling rate, greater the number of 1421 bond-type, greater the proportion occupied by fcc in the mixed crystal. At the same time, it is found that the variation of the mean coordination number of atoms is closely related to that of 1551, 1441, 1661　bond-types, which reflects that the varying rule of the symmetric configurations in the system is related to the variation of the coordination number. In visualized analysis, the amorphous and crystal structures in 2D cross sections and the concrete structures of both the basic clusters of fcc and hcp in 3D were displayed by means of center-atom method.