Effect of alloying elements on lattice misfit and elasticities of Ni-based single crystal superalloys by first-principle calculations

The site occupancy, lattice misfit and elastic modulus of Ni-based single crystal superalloys are investigated by combining the first principles exact muffin-tin orbital method and coherent-potential approximation. The site preference of alloying elements in γ′-Ni3Al can be classified into four types: Co, Fe, Ru and Ir occupy Ni site or Cr, Mo, Re, Ti, V occupy Al anti-site (namely alloying elements occupy Al site while the removed Al occupy Ni site). Ti and V are the alloying elements which stabilize the γ′-Ni3Al. The lattice misfit and the difference of elastic properties between γ and γ′ phases are the causes of γ′ rafting, while the alloying elements will improve the differences. The effects of 1 at. % ~5 at. % alloying elements on lattice constant and misfit are studied, because of biggish atomic radius, Ir, Mo, Ti, Re and Ru increase the lattice constant of γ/γ′ phase much faster, and the alloying elements have some impacts on the lattice misfit of γ/γ′ phase. Re is the most remarkable alloying element which improves the elastic modulus of Ni-based superalloys. •Four site preference of alloying elements in γ′-Ni3Al.•1 at. %~5 at. % alloying elements effect on lattice constant and misfit.•The effects of lattice misfit and elasticity on γ′ rafting with alloying elements.•Ti and V stabilize the γ′ phase.