Enhancing adhesion of Al₂O₃ scale on Ti-Al intermetallics by alloying: A first principles study

The influence of V, Cr, Nb, Mo, Ta, and W alloying elements on the stability and adhesion properties of γ-TiAl(111)/Al₂O₃(0001) and the α₂-Ti₃Al(0001)/Al₂O₃(0001) interfaces are studied via first principles calculations. All the considered alloying elements prefer to substitute for the Ti site in both the γ-TiAl(111) and the α₂-Ti₃Al(0001) surfaces, with occupation energy differences of more than 0.2 eV and 1.0 eV lower than Al site, respectively. The interfaces studied here own negative formation energy except the Cr alloyed γ-TiAl/Al₂O₃ system. The alloying elements will enhance the bonding interactions of the α₂-Ti₃Al/Al₂O₃ interfaces and maintain the strength of the γ-TiAl/Al₂O₃ interfaces, most of the alloyed interfaces own work of adhesion of lower than −2.5 J/m². Different charge transfer behaviors between Al₂O₃ scale and Ti-Al intermetallics is probably the major factor that enhancing the adhesion of the considered systems.