High-temperature oxidation mechanisms of nano-/submicro-scale lamellar structures in an intermetallic alloy

摘要

The aim of this study was to elucidate the oxidation mechanisms of gamma-TiAl/alpha(2)-Ti3Al lamellar structures in a TiAlNbCr intermetallic alloy at a high temperature. The original gamma-TiAl/alpha(2)-Ti3Al lamellae in the alloy were transformed into H-Ti2AlN/alpha(2)-Ti3Al lamellae, and kappa-Al2O3, alpha-Al2O3 and some remaining gamma-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 kappa-Al2O3 can be converted into the stable alpha-Al2O3. TiN and Ti2AlN could be converted into each other to form kappa-Al2O3 under specific conditions. Thus the oxidation path of the intermetallic alloy is established as follows: gamma - TiAl -> (H - Ti2AlN,TiN) -> kappa - Al2O3 -> alpha - Al2O3. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.