| Ti-Al intermetallic alloys are considered to be some of the most potentially important structural materials for applications in aerospace and automobile industries. However, the high-temperature oxidation resistance problem limits its application. Its surface oxidation problem has recently received significant attention. Based on the first principles, we study the adsorption of chlorine on the y-TiAl(100) and a2-Ti3Al(0001) surfaces, and discuss its effects on the surface oxidation of Ti-Al intermetallics.Firstly, the adsorption of chlorine on y-TiAI(100) surface is studied. The results show the most stable adsorption site is HFb surrounded by four metal atoms. The adsorption energy per chlorine atom increases when the coverage increases, so the adsorption reaches saturated rapidly. The bonds formed by chlorine and metal atoms are ionic, and chlorine is more likely to interact with titanium rather than aluminum. The co-adsorption of chlorine and oxygen atoms on y-TiAl(100) surface is also investigated. The adsorption energy of oxygen atoms is increased by the adsorption of chlorine, and there are competitions between the adsorption of the chlorine and the oxygen atoms. So that the coverage of oxygen atoms will be decreased. Therefore, chlorine can weaken the oxidation of y-TiAl(100) surface.Then we studied the adsorption of chlorine on a2-Ti3Al(0001) surface. The results are similar to those on the γ-TiAl(100) surface. Compared the adsorption of chlorine on γ-TiAl(100) and a2-Ti3Al(0001) surface, it can be found that the adsorption is more stable on α2-Ti3Al(0001) surface, and the chlorine treatment is more effective on α2-Ti3Al(0001) surface.In a word, the adsorption of chlorine increase the adsorption energy of oxygen on both γ-TiAl(100) and α2-Ti3Al(0001) surfaces and decrease its coverage. These may be the reason why chlorine can increase the oxidation resistance ability of Ti-Al intermetallics. |
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