Energetics and electronic structure of Re and Ta in theγ′phase of Ni-based superalloys

Abstract

By use of first-principles methods based on density functional theory, we study the alloying effect of Re and Ta in the ${\gamma }^{\prime }$ phase of Ni-based superalloy. We find that when Re (Ta) is substituted for Al, the binding energy of the system obtained by the DMol method decreases by 2.55 eV (4.04 eV). This is accompanied by a small local lattice distortion (less than 1% of the calculated lattice constant). In contrast, when Re (Ta) is substituted for Ni, the binding energy of the system decreases by only 0.68 eV (1.11 eV), but there is a larger local lattice distortion (more than 3% of the calculated lattice constant). The transfer energies obtained by the DMol method show that both Re and Ta exhibit a strong Al site preference, which is in agreement with experimental and recent theoretical results. Using the discrete variational method, we calculate the interatomic energy, the charge distribution and the partial density of states. Both Re and Ta in the ${\gamma }^{\prime }$ phase can strongly enhance the interatomic interaction between nearest neighboring atoms, as well as that between a nearest neighboring atom and the associated next nearest neighboring atom. However, the bonding between Re (Ta) itself and the host atoms is weak. We also examine the strong dependence of the binding energy on the substitution type by analyzing the interatomic energies, and discuss the charge distribution and the partial density of states for the systems in which Re (Ta) is substituted for Al.