Theoretical study on the effects of alloying elements on oxygen-adsorption properties of the Ti2AlNb surface

Ti2AlNb-based alloys own excellent mechanical properties and have great application potential in aero-engine. However, their high temperature oxidation resistance should be improved for long-serving process. Alloying is one of the most effective ways to improve their oxidation resistance properties. The substitution stability and segregation property of the alloying elements on the Ti2AlNb surface are first studied via first principles calculations. Twelve alloying elements of the Si, Sc, V, Cr, Mn, Fe, Y, Zr, Mo, Hf, Ta and W are considered in this work. The effects of alloying elements on the oxygen adsorption properties of Ti2AlNb surface are then studied. The Si, Sc, Y, Zr and Hf elements prefer to occupy the surficial slab indicating a strong segregation phenomenon, while others have not such a tendency. The influence of these alloying elements on the adsorption behaviors of oxygen atom on the Ti2AlNb surface was calculated. It was found that the adsorption energy of oxygen increased in alloying element contained system comparing with the undoped system. It is most obvious when the alloying element substitution for the Ti, the adsorption energy increase more than 0.5 eV. The alloying elements can help to inhibit the adsorption of oxygen on Ti2AlNb surface by affecting the bonding characteristics of oxygen, and thereby improving the oxidation resistance of the alloy.