Segregation of tungsten at γ'(L12)/γ(fcc) interfaces in a Ni-based superalloy: An atom-probe tomographic and first-principles study

gamma(fcc)/gamma(')(L1(2)) heterophase interfaces in a Ni-based superalloy are investigated using atom-probe tomography and first-principles calculations. Flat {100} interfaces exhibit a confined (nonmonotonic) Gibbsian interfacial excess of tungsten, Gamma(W)=1.2 +/- 0.2 nm(-2), corresponding to a 5 mJ m(-2) decrease in interfacial free energy. Conversely, no measurable segregation of W is detected at curved interfaces. First-principles calculations for a Ni-Al-W system having a {100} interface indicate a decrease in the interfacial energy of 5 mJ m(-2) due to W segregation. Similar calculations for {110} and {111} interfaces predict an increase of 1 and 9 mJ m(-2) in their energies, respectively, and therefore no heterophase segregation.