Molecular Dynamics Study of Phosphorus Migration in Σ3(111) and Σ5(0-13) Grain Boundaries of α-Iron

Abstract

Phosphorus atoms in steels accumulate at grain boundaries via thermal and irradiation effects and induce grain boundary embrittlement, which is experimentally confirmed by an increase in the ductile-brittle transition temperature. Quantitative prediction of phosphorus segregation at grain boundaries under various temperature and irradiation conditions is essential for preventing embrittlement. To develop a model of grain boundary phosphorus segregation in α-iron, we studied the migration of a phosphorus atom in two types of symmetrical tilt grain boundaries (Σ3[1-10](111) and Σ5[100](0-13) grain boundaries) using molecular dynamics simulations with an embedded atom method potential. The results revealed that, in the Σ3 grain boundary, phosphorus atoms migrate three-dimensionally mainly in the form of interstitial atoms, whereas in the Σ5 grain boundary, these atoms migrate one-dimensionally mainly via vacancy-atom exchanges. Moreover, de-trapping of phosphorus atoms and vacancies was investigated.

Segregation of Phosphorus and Silicon at the Grain Boundary in Bcc Iron via Machine-Learned Force Fields

“…The prediction of the interstitial site as the preferred segregation site of P at ∑5(310) GB in iron is in agreement with experimental observations [2]. Our E seg profile in Figure 5 is in good agreement with recent calculations of the trapping energy by Ebihara and Suzudo [39] based on the embedded atom method. Lejček et al [10] calculated the binding energy of phosphorus in the interstitial and substitutional sites in the [310] GB plane in bcc Fe as a function of the lattice parameter.…”