Atomistic simulation of phosphorus segregation to 3 (111) symmetrical tilt grain boundary in -iron

Irradiation-induced grain boundary (GB) phosphorus segregation is an important factor for estimating the embrittlement of nuclear reactor pressure vessel steels, but the physical process of phosphorus migration to grain boundaries is still unclear. We numerically studied phosphorus migration toward a 3(111) symmetrical tilt GB in -iron using molecular dynamics. We found that, in the vicinity of the GB within ∼1 nm distance, an iron-phosphorus mixed dumbbell and an octahedral interstitial phosphorus atom push a self-interstitial atom into the GB, and the phosphorus atom becomes a substitutional atom. A phosphorus-vacancy complex in the region also becomes dissociated, and the vacancy is absorbed in the GB without dragging phosphorus. The results claim that a novel view of the segregation process is required.