Molecular Dynamics Simulations of Phosphorus Migration in a Grain Boundary of alpha-Iron

K Ebihara and T Suzudo, TMS 2020 149TH ANNUAL MEETING & EXHIBITION SUPPLEMENTAL PROCEEDINGS, 995-1002 (2020).

DOI: 10.1007/978-3-030-36296-6_93

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 Sigma 3(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.

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