Effect of solute segregation on the intrinsic stacking fault energy of Co-based binary alloys: A first-principles study

Abstract Segregation of solute atoms to stacking faults (Suzuki segregation) and their interactions are of longstanding attention since it has a deep impact on mechanical properties. In this study, we systematically investigate the segregation behavior of different solute atoms in fcc Co-based binary alloys and its effect on the intrinsic stacking fault energy (SFE) using first-principles density-functional-theory (DFT) calculations. Interestingly, while Mo, W, Cr, Mn and Al atoms have a strong tendency to Suzuki segregation with some significant energy barriers, Ni atom has no tendency of segregation and only Fe atom has extremely low energy barriers. A strong segregation effect on the intrinsic SFE was observed and it only extends at a few atomic layers in the vicinity of the intrinsic stacking fault plane. The results are consistent with observed solute segregation in similar alloys and commercial superalloys then it would be useful for SFE modeling and Co-based alloys design. Furthermore, the effect of solute concentrations and changes in the electronic features (charge density difference and density of states) are also investigated. A mutual interaction between solutes and stacking faults enhanced local bonding between the solute atom and the adjacent Co atoms, resulted in the lower intrinsic SFE, thus favoring Suzuki segregation.