Atomistic simulation of phosphorus segregation to Σ3 (111) symmetrical tilt grain boundary in α-iron

Abstract

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 Σ3(111) symmetrical tilt GB in α-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.

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

“…Moreover, the rate theory model incorporates the model of trapping and de-trapping P atoms at GBs, and therefore, GB P segregation evaluated by the model can be compared with experimental measurement [16]. The trapping process is incorporated into the model based on the result of molecular dynamics (MD) simulations, in which a pair consisting of a P atom and a self-interstitial atom or a P atom and a vacancy dissociates before reaching a GB [17,18]. However, an intuitive, simple model is used for the de-trapping process, and hence a more detailed model is necessary.…”

Effect of Grain Boundary on Diffusion of P in Alpha-Fe: A Molecular Dynamics Study

“…The diffusion phenomenon of the defects and solute elements around the GBs has long been an area of intrigue for the researchers due to its impact on various mechanical properties, such as; corrosion resistance, and embrittlement [9]. The tempered embrittlement and radiation embrittlement has been observed in steel during rapid cooling from higher temperature and irradiation [10]. Phosphorus is one of the major impurity amongst the embrittlement species in steel [10][11][12].…”

“…The tempered embrittlement and radiation embrittlement has been observed in steel during rapid cooling from higher temperature and irradiation [10]. Phosphorus is one of the major impurity amongst the embrittlement species in steel [10][11][12]. The Phosphorus grain boundary segregation plays an important role in the intergranular embrittlement of the reactor pressure vessel (RPV), especially under irradiation enhancing diffusion [11,13].…”

“…Although, numerous experimental and atomistic simulations have already been performed on the Phosphorus diffusion in the GBs of alpha-Fe, their trapping effect mechanism has not been considered frequently [9,10,12,14,15,19,22,23]. Henceforth, it is of great significance to research and explore the fundamental mechanism of the P segregation in the GBs [19,24].…”