Influence of interatomic interactions on the mechanical properties of face-centered cubic multicomponent Co-Ni-Cr-Mo alloys

The composition of a multicomponent solid solution has a significant influence on its mechanical and microstructural properties. Herein, the microstructures, phase stabilities, mechanical properties, and interatomic interactions of multicomponent Co-(5-55)Ni-19Cr-9Mo (mass%) alloys with varying Ni contents were comprehensively investigated. First-principles calculations were performed to predict the mechanical properties, electron distributions, atomic bonding states, and density of states of the alloy system. The local charge distribution revealed that the alloying elements exhibit stronger bonds with Co atoms than with Ni atoms, and the Ni-Ni bond is the weakest; accordingly, an increase in the Ni content generally diminishes the interatomic interactions in the studied alloy system. Meanwhile, significant augmentations in the strength and elastic modulus were observed at 45 mass% Ni. This was attributed to the additional interactions that are prevalent in 45 and 55 mass% Ni alloys that stem from the second-nearest Ni atoms with vacant 3d states and involve Co, Cr, and Mo atoms. Strengthening analyses indicated that the shear moduli predetermined the changes of yield strength with respect to the Ni contents. The stacking fault energies (SFEs) were calculated ab initio at 0 K and thermodynamically at 1500 K. A similar trend in the SFE variations was obtained under special consideration of the concentration dependence of the Co-Ni interaction, which indicated the significant influence of interatomic interactions even at elevated temperatures.