Effect of vacancies on the nucleation of Cr precipitates at grain boundary in α-Fe

Effect of local vacancies on the nucleation of Cr precipitates at Σ3 ⟨110⟩ {112} grain boundary (GB) in α-Fe has been studied using molecular dynamics with a two-band embedded atomic model potential. Radiation-induced vacancies and Cr atoms were directly introduced into the GB core. The local vacancies affect the accumulation of Cr atoms and the evolution of the GB. It is of interest to find that high vacancy concentrations enhance the long-distance migration of Cr, which is mainly correlated to the vacancy migration mechanism, thus leading to the formation of large vacancy-diluted Cr precipitates near the GB plane. Also, the large vacancy clusters are found to be depleted by Cr atoms during relaxation. The accumulation of vacancies and nucleation of Cr precipitates at the GB lead to significant deformation of the GB structure, resulting in the displacement and broadening of the GB. Without vacancies, the GB tends to climb perpendicular to the GB axis. The current research could help in understanding the nucleation mechanism of Cr precipitates at the GB in α-Fe.