Microstructure of Liquid Co50Ni50 During Rapid Solidification.

Abstract

The rapid solidification process of Co50Ni50 alloy was simulated by molecular dynamics method, and the formation and evolution characteristics of cluster structure in the solidification process were analyzed by the pair distribution function, Honeycutt-Andersen bond type index method and the largest standard cluster. The results show that during the solidification process with a cooling rate of 1×1012 K·-1, the probability of mutual bond formation between Co-Co atoms is always greater than that of Ni-Ni, and the formation of the 1421 bond type is dominant in the crystalline structure. The inflection point of the characteristic bond type 1421 varies with the crystalline transition temperature Tg of the system. The Co-Ni alloy is mainly composed of a face-centered cubic atomic group composed of the 1421 bond type. Meanwhile, there will also be a small amount of hcp structure and a smaller amount of bcc structure. Further analysis revealed that the formation of the fcc structure requires the fast decomposition of TCP structures (at 1450 K). That is to say, the TCP structure must be disassembled before the fcc structure is formed. These findings are useful to provide important guidance for the crystallization of Co50Ni50 alloy under rapid cooling in the experiment.