Quantitative prediction of Suzuki segregation at stacking faults of the γ' phase in Ni-base superalloys

Recent experiments suggest that Suzuki segregation may play an important role during deformation in Ni-base superalloys at intermediate temperatures. In this study, a segregation isotherm model incorporating segregation enthalpy from ab initio calculations is proposed to predict quantitatively solute enrichment at superlattice intrinsic stacking faults (SISF) within the gamma' precipitates in Ni-base superalloys. A sublattice model is employed to describe the gamma' phase. A strong correlation between segregation enthalpy and solute enrichment is found. Even though the segregation enthalpy is relatively small, the predicted solute enrichment is consistent with experimental observations. The simulation predictions also suggest a strong cross-correlation among different alloying elements. For example, it is found that segregation of Co on the Ni sublattice at the fault draws segregation of Cr that has a positive segregation enthalpy at the fault without the presence of Co. Such quantitative predictions of equilibrium segregation of solutes at stacking faults in gamma' precipitates and its effect on the stacking fault energy could aid the investigation of deformation mechanisms and help the design of superalloys. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.