LAUSR

Abstract The aim of this study was to elucidate the oxidation mechanisms of γ-TiAl/α2-Ti3Al lamellar structures in a TiAlNbCr intermetallic alloy at a high temperature. The original γ-TiAl/α2-Ti3Al lamellae in the alloy were transformed into H-Ti2AlN/α2-Ti3Al lamellae, and κ-Al2O3, α-Al2O3 and some remaining γ-TiAl phases were observed to be co-existent. The first-principles calculations of density-functional type based on the generalized-gradient approximation revealed that the metastable κ-Al2O3 can be converted into the stable α-Al2O3. TiN and Ti2AlN could be converted into each other to form κ-Al2O3 under specific conditions. Thus the oxidation path of the intermetallic alloy is established as follows: γ − TiAl → (H − Ti2AlN, TiN) → κ − Al2O3 → α − Al2O3.