Theoretical study of the effects of alloying elements on TiO₂/Ti₂AlNb interface adhesion properties

Ti₂AlNb-based alloys are expected to be applied in the manufacture of parts of aeroengines to achieve the goal of increasing the thrust-to-weight ratio. However, the poor high temperature oxidation resistance of these alloys may hinder their applications. Alloying has been proven to be effective in improving oxidation resistance properties. However, the selection of alloying elements and their influence mechanisms are rarely studied. The TiO₂/Ti₂AlNb interface bonding interactions and the effects of alloying elements of Si, Sc, Y, Zr, Mo and Hf were investigated via first principles calculations. The separation energy and electronic structure were studied to explore the bonding interactions between the oxide scale and Ti₂AlNb matrix. When Zr and Hf are used to replace Al, the bonding properties of the TiO₂/Ti₂AlNb interface are improved. The tensile and shear deformations of the interfacial zones are applied to study the influence of alloying elements on the TiO₂ oxide spalling on Ti₂AlNb. The tensile strength is increased by more than 2 GPa when Nb is substituted by the Sc, Zr and Hf elements. Therefore, Sc, Zr, and Hf are beneficial for inhibiting oxide spalling and will have great potential to improve the oxidation resistance properties.