Modeling solute-vacancy trapping at oversized solutes and its effect on radiation-induced segregation in Fe–Cr–Ni alloys

Rate theory modeling was used to simulate the effects of oversized solute additions on radiation-induced segregation in austenitic stainless steels. The purpose was to understand the effects of a solute-vacancy trapping mechanism on radiation-induced segregation and to define key parameters that most affect segregation behavior. Sensitivity analysis of the model showed the solute-vacancy binding energy to be the most important model parameter. Binding energies from ab initio first principles were calculated for oversized solutes of Pt, Ti, Hf and Zr, with energies of 0.31, 0.39, 0.71 and 1.08 eV, respectively. Differences in binding energies, despite similar sizes of the atoms, suggests that the short-range electronic interactions play an important role in determining binding energy. The model results show oversized solutes to be most effective at reducing grain boundary Cr depletion at temperatures of 450–500 °C for a dose rate applicable to proton irradiations. The reduction increases with increasing oversized solute concentration, where it saturates at approximately 0.1 at.%.