Nb-Ti-Al合金高温氧化机理电子理论研究

采用递归法计算了Nb合金的电子态密度、原子镶嵌能、亲和能和团簇能等电子结构参数,研究Nb合金高温氧化机理.研究表明,氧在Nb合金表面的吸附能较低,易在合金表面吸附,并逐渐扩散到Nb合金的基体中.氧在合金基体中镶嵌能为负值,氧的态密度和Nb相似,在Nb中具有很高的溶解度.Ti,Al在合金晶内的镶嵌能均高于各自在合金表面的镶嵌能,Ti,Al从合金内部向合金表面扩散,最终在Nb合金表面偏聚,形成富Ti,Al的表层.团簇能计算结果表明Nb合金表面的Ti,Al原子各自均有聚集倾向,分别形成Ti和Al原子团.氧与合金

Electronic theory study on high temperature oxidation mechanism of Nb-Ti-Al alloy

The electronic structure parameters of density of electronic states, atoms embedding energy, affinity energy and cluster energy of Nb alloy have been calculated using the recursive method. The high-temperature oxidation mechanism of Nb alloy was investigated. Studies show that the oxygen adsorption on Nb alloy surface can lower the adsorption energy, so oxygen is easily adsorbed on the alloy surface, and gradually diffuses into the Nb alloy matrix. Oxygen has a high solubility in the Nb alloy matrix because of the negative atom embedding energy, and it has similar density of states to Nb. Because the atom embedding energies of Ti and Al in the alloy matrix are higher than that on the alloy surface, Ti and Al atoms diffuse from the alloy matrix to the alloy surface and segregate on the alloy surface, ultimately making the Nb surface rich in Ti and Al. The clustering energy calculation shows that Ti and Al atom tend to gather on their own area, forming Ti and Al atom clusters respectively. Oxygen can interact with Nb, Ti and Al because of the negative affinity energy with Nb, Ti and Al on Nb alloy surface, to generate the Nb₂O₅, TiO₂ and Al₂O₃ mixed oxide film which has protective effect on Nb alloy.