Multiscale modeling of point defect interactions in Fe–Cr alloys

Predictive performance models of ferritic/martensitic alloys in fusion neutron irradiation environments require knowledge of point defect interactions with Cr, which can be investigated by a multiscale modeling approach. Molecular dynamics simulations, using Finnis–Sinclair-type potentials, have been used to investigate the interstitial diffusion and reveal that the extremes of attractive and repulsive binding between Cr and interstitials change the characteristics of interstitial migration and the Cr-to-Fe diffusivity ratio. Ab-initio calculations have been performed to determine the vacancy–Cr interactions, and these calculations reveal complex electronic and magnetic interactions between Cr and Fe. The ab-initio values have been used to calculate the Cr-to-Fe diffusivity ratio by a vacancy mechanism using the LeClaire multi-frequency model and a kinetic lattice Monte Carlo model, both of which indicate that Cr diffuses faster than Fe. The modeling results are discussed in the context of the radiation-induced segregation of Cr at grain boundaries in BCC Fe–Cr alloys.