Effect of Re in γ phase, γ′γ′ phase and γ/γ′γ/γ′ interface of Ni-based single-crystal superalloys

Molecular dynamics (MD) within the framework of the embedded atom method and the first-principles discrete variational method (DVM) are both used to study the effect of Re in the γ   phase, the γ′γ′ phase and the γ/γ′γ/γ′ interface of Ni-based single-crystal superalloys. From the MD relaxation it is found that the γ/γ′γ/γ′ interface only has two atomic configurations, i.e. a coherent region and a misfit dislocation region, and the “cage-like” misfit dislocation networks, consist of 〈110〉{0 0 1} edge dislocations winding over the precipitate phase. The MD results also show that the substitution atom Re stabilizes both the γ   phase and the γ′γ′ phase, and influences the degree of mismatch between γ   and γ′γ′. From the simulation results we find that Re atoms have a tendency to cluster in both the γ   phase and the γ′γ′ phase. Based on the MD simulation we have chosen six clusters of the γ/γ′γ/γ′ interface for the DVM study, in which the interatomic energy, the charge distribution, the partial density of states and the electron density difference are all calculated. It is found that a Re atom occupying either a Ni site in the γ   phase or an Al site in the γ′γ′ phase can strongly enhance the bonding strength between Re and its nearest neighboring atoms, suggesting that the substitution atom Re will influence dislocation motion along the γ/γ′γ/γ′ interface.