Effects of alloying elements concentrations and temperatures on the stacking fault energies of Co-based alloys by computational thermodynamic approach and first-principles calculations

The atomic-scale microstructural and compositional modification of materials are one of the most promising developments of modern materials science. In the present study, we investigate the stacking fault energy (SFE) variations of binary Co-based alloys with different alloying elements (Cr, W, Mo, Ni, Mn, Al and Fe) and concentrations (from 0 to 20 at.%) over a broad range of temperatures (from 0 to 1000 K) by computational thermodynamic approach and first-principles density-functional-theory (DFT) calculations combined with quasi-harmonic approximation (QHA). Our work presents a fundamental understanding of the theoretical SFE calculation and the deviations involved in computational thermodynamic approach and first-principles calculations systematically for the first time. It concludes that the SFEs of binary Co-based alloys are increased as the increased of temperature, Ni, Mn, Al and Fe concentrations while the SFEs are decreased as the increased of Cr, W and Mo concentrations qualitatively. Quantitatively, the SFE differences of these two methods are relatively small (lower than 27 mJ/m2). The SFE variations can be explained regarding the charge density distributions and the atomic bonding. These results also highlight the critical role of Suzuki effect and the key for the SFE variations is the alloying elements only in the vicinity of the fault plane.