多元合金化对γ-TiAl(111)表面氧吸附影响机理的第一原理研究

First-principles study on the influence of alloying when oxygen absorption on the surface of γ-TiAl(111)

采用基于密度泛函理论的赝势平面波第一原理方法,研究了合金化对γ-TiAl合金(111)表面氧吸附的影响机理。结果表明,氧于γ-TiAl基合金表面的吸附是化学吸附,Nb与Si共同掺杂使吸附更容易发生。氧与表面Al和Ti间同时存在共价和离子键作用。且总的作用差别并不大,这就使得TiAl金属间化合物氧化时,能够同时生成TiO2和Al2O3。同时Si直接与氧发生氧化生成的SiO2与Al2O3层一起阻碍内氧化的进行。Nb、Si共同掺杂时,Nb主要在基体中起作用,Si主要在表面起作用,两种作用可以叠加,即Nb、Si共同掺杂比单独添加使γ-TiAl合金具有更高的抗氧化性能。

A first-principles plane-wave pseudo potential method,based on the density functional theory,was used to investigate the influence of alloying elements on oxidation and its influence mechanics of γ-TiAl alloy.Study shows that the absorption of oxygen on the surface of γ-TiAl based alloy is chemical absorption.Nb and Si codoping will make the absorption much easier.There are both covalent and ionic bond between oxygen and Al,Ti.And there is a little difference in total effect,which enable the generation of TiO2 and Al2O3 simultaneously,when the intermetallic compound oxidizes.Meanwhile,silicon would react with oxygen directly,and form SiO2 which can prevent the internal oxidation together with Al2O3.Niobium is effective mainly in the bulk,while silicon is on the surface,when doping them at the same time,and these two effects would combine together,that is,doping both niobium and silicon will make the oxidation resistance of γ-TiAl based alloy much better than doping those elements separately.