Atomic computer simulation of the formation and growth process of Cu-precipitate in Fe-Cu alloy

We focus on nanoscale copper-rich precipitates and try to clarify the effect of the nanoscale copper-rich precipitates on embrittlement of reactor pressure vessel steels. Our final goal is to evaluate such embrittlement from microscopic viewpoint based on atomistic simulation. In this study, we propose Multi Vacancy Lattice Monte Carlo (MVLMC) method which can analyze the model that has more than one vacancy. We showed that process of copper clustering consists of the two phases, i.e., formation phase, and combination phase. And, we analyzed a combination process of a cluster using MVLMC in detail, and evaluate formation of a cluster using distance between clusters. It is noted that in combination between a nano cluster smaller than 1 nm and a cluster of about 2 nm, minute nano clusters separate from the former cluster and are absorbed by the latter cluster. Moreover, we found that a nano cluster is formed by distance of about 1.5 nm extent from other clusters in a formation process of a cluster and that distance between clusters of about 2 nm is about 10 nm. (orig.)