Simulation for temperature dependence of irradiation-induced grain-boundary phosphorus segregation using first-principles-based rate theory model

Ebihara, Kenichi   ; Suzudo, Tomoaki   ; Yamaguchi, Masatake   ; Nishiyama, Yutaka 

Since grain-boundary (GB) embrittlement by phosphorus (P) under irradiation is a crucial problem in steels, it is necessary to evaluate irradiation-induced P GB segregation in order to secure the integrity of nuclear structural materials. Recently, partial diffusion coefficients including the vacancy (V) drag effect, which are obtained by the kinetic Monte Carlo method incorporating the barrier energy estimated by the first-principles calculation, are built into the diffusion rate model, and the model is applied to the evaluation of the P GB segregation. Since the amount of V is affected by temperature, we evaluated the P GB segregation by the model. As a result, although the model could not simulate the increase of P GB segregation in the high temperature region which is shown by the McLean's diffusion model, the model incorporating the process of capturing and releasing P at GB simulated the increase. Hence, such a process is significant for simulating the temperature dependence.