First Principles Study Of γ-TiAl / TiO _{2 Electronic Structure And Alloying Elements} Interface Of Its Impact

As prospective structural materials for applications in aerospace and automobile industries, γ-TiAl is one of the most widely investigated materials. In this paper, the structural stability and cohesion of the γ-TiAI/TiO2interface are investigated by the first-principles calculations. The effects of the alloying elements Nb and Si on the interface are investigated, and the reasons of the improvement on the oxidation resistance by the alloying are also discussed.Based on our calculation, two interface models of γ-TiAl (111)/TiO2(110) have been constructed. Their cohesive energies have been calculated, and their values are1.86J/m2,1.90J/m2, respectively. Comparing with interfaces between other metal and oxides, the strength of the γ-TiAl (111)/TiO2(110) interface is poor. When they are stretched vertically to the interface, the interfaces are not fractured at the interfaces. Instead, the bonds between the outmost oxygen atom and the Ti atom belonging to the TiO2are broken. Two new surfaces, TiO2(110) with oxygen vacancy and γ-TiAl(111) with oxygen adsorption, are formed. From the electronic structures, it can be found that the formation of new fracture surfaces is due to the strong interactions between the O atoms in TiO2and the metallic atoms on TiAl surfaces.Furthermore, the effects of the alloying elements Nb and Si on the cohesive strength of the γ-TiAI/TiO2interface are investigated. The results show that the effect of Nb on the interface is insignificant, and this may be caused by the favorable site of Nb which keeps a long distance from the interface. While, the doped Si atom prefers the site to replace the Al atom in TiAl, and improves the cohesive strength of the interface significantly. For the Si-doped system, the stronger interaction between the Si atom and metallic atoms results in the stronger interfacial bonds and inhibits the spallation of oxide scale. Thus, we infer the enhancement of the interface cohesion between TiAl and TiO2by Si doping may be one of the reasons why Si improves the oxidation resistance of TiAl.