First-principles study on the NiAl/Al2O3 interfacial segregation of Hf during the oxidation of Hf-modified NiAl

Despite the well-known beneficial effect of reactive element dopants on improving oxidation resistance alumina-forming alloys, many open questions remain, including migration and segregation elements at oxide/alloy interface, a key zone in controlling global kinetics interface adhesion. Herein, we elucidate atomic processes governing interfacial dynamics hafnium with γ-Al2O3 θ-Al2O3, two dominant metastable phases before transforming to stable α-Al2O3 during Ni-Al alloys. Our results show that Al vacancies Al2O3 overlayer play critical role influencing Hf atoms HfO2 formation. For (0 0 1)/NiAl (1 0) presence drives aggregation from NiAl substrate, resulting nucleation HfO2. By contrast, for θ-Al2O3 0)/NiAl steers substrate across deeper into oxide lattice, promoting formation bulk layer. These may find broader applicability manipulating transport process by phase stoichiometry transient phases.