On the tungsten segregation at γ/γ′ interface in a Ni-based single-crystal superalloy

Through a combination of atom probe tomography (APT) and theoretical calculations, the distributions of tungsten (W) at the γ/γ′ interfaces with exposure effects in a Ni-based single crystal superalloy are investigated. W shows the reversal partitioning behavior during long-term thermal exposure, partitioning from γ-matrix to γ′-precipitates, accompanied by varying lattice misfit. The APT results show that the γ/γ′ interface in all samples possesses a Gibbsian interfacial excess, corresponding to decrease in interfacial energy. The elemental segregation demonstrates high dependency on elastic strain energy, calculated according to lattice misfit. The driving force for the interfacial segregation is the release of elastic strain energy.