A first-principles survey of γ/γ′ interface strengthening by alloying elements in single crystal Ni–base superalloys

The strengthening effects induced by alloying elements on γ/γ′ interface in single crystal (SC) Ni–base superalloys have been investigated using first-principles quantum mechanics DMol3 calculations. The charge density difference indicates that a strong anisotropic bonding forms between the first-nearest alloying metal and Ni atoms due to alloying metal-d/Ni-d hybridization. The bond orders (BO) for a local environmental cluster are proposed and calculated to describe the cohesion and shear strength of γ/γ′ interface, respectively. Larger bond-order values represent stronger interfacial cohesion and shear strength. Our calculations show that alloying elements significantly increase the net vertical and horizontal bond-order values, with Mo yielding the most effective cohesive strength, while W yielding the most effective shear strength. A complete order of strengthening effects is presented for alloying elements that are typically added in SC superalloys.