First-principles study of the bonding characteristics of TiAl(111)/Al2O3(0001) interface

Abstract First principles calculations were carried out for α-Al 2 O 3 (0001) surface and γ-TiAl(111)/α-Al 2 O 3 (0001) interface to study the adhesion properties of the interface and to clarify the mechanisms that govern the adhesion of TiAl and its oxidation product Al 2 O 3 . Two type interface models, the TiAl(111) with Al- and O-terminated α-Al 2 O 3 (0001) surfaces denoted as T(A 1 )-type and T(O T )-type interface, respectively, were considered. The Universal Binding Energy Relation (UBER) was used to determine the separation between TiAl and Al 2 O 3 and the work of adhesion of the γ-TiAl(111)/α-Al 2 O 3 (0001) interface. Optimization was then performed for all interfaces considered here using the separation obtained with UBER. The lowest work of adhesion is −1.05 J/m 2 for the T(A 1 )-type interface and is −4.04 J/m 2 for the T(O T )-type interface. There exists competition between O–Ti and O–Al (on the TiAl side) interactions; however O–Al bond is stronger than O–Ti bond because the main body of the Al valences is involved in the hybriding with O p electrons, while only part of the Ti d valence is involved in the O–Ti bonding. Thus the O–Al interaction dominates the adhesion between TiAl(111) and Al 2 O 3 (0001) surfaces, and it can be inferred that an Al-rich TiAl surface will favor the adhesion between TiAl/Al 2 O 3 .