Phase partitioning and site-preference of hafnium in the γ′(L12)∕γ(fcc) system in Ni-based superalloys: An atom-probe tomographic and first-principles study

Atom-probe tomography (APT) and first-principles calculations are employed to investigate the partitioning of Hf in the γ′(L12)∕γ(fcc) phases in two multicomponent Ni-based superalloys. APT results indicate strong partitioning of Hf atoms to the γ(fcc)-phase. We perform first-principles calculations of the substitutional formation energy of Hf for a model γ(Ni)∕γ′(Ni3Al) system indicating Hf partitioning to the γ′-phase. Additional calculations of the Hf–Cr binding energy suggest, however, that Cr atoms, which partition to the γ-phase, have a strong attractive binding energy with Hf atoms, thus predicting a reversal of the Hf partitioning in favor of the γ-phase due to alloying with Cr.