Molecular Dynamics Simulations of Phosphorus Migration in a Grain Boundary of α-Iron
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Phosphorus causes steels grain boundary embrittlement, which is considered to influence the ductile-brittle transition in reactor pressure vessel steels. In order to develop a rate theory model for calculating grain boundary phosphorus segregation based on atomistic processes, so far, we have evaluated the diffusion coefficient of phosphorus migration due to dragging by vacancies and self-interstitial atoms and the influence of thermal grain boundary fluctuation and of strain around grain boundaries to the phosphorus migration. However, the atomistic process that phosphorus atoms de-trap from grain boundaries, which is essential to the rate theory model, is still unclear. In this study, we simulated the migration of a phosphorus atom in the region of a Σ3(111) symmetrical tilt grain boundary using molecular dynamics and evaluated the migration barrier energy. From the results, we found that phosphorus atoms can migrate through gaps between iron atoms inside the grain boundary region.
KeywordsGrain boundary Phosphorus segregation Molecular dynamics simulation Trapping and de-trapping Phosphorus migration
This work is partly supported by JSPS KAKENHI Grant Number JP15K06429.
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