影响Nb替位掺杂γ-TiAl基合金延性的电子性质因素  

Electronic Properties Influencing Ductility of Nb-Substituted γ-TiAl Based Alloys

作　　者：宋庆功 赵俊普[1] 顾威风 甄丹丹 郭艳蕊[1] 李泽朋 Song Qinggong;Zhao Junpu;Gu Weifeng;Zhen Dandan;Guo Yanrui;Li Zepeng(Institute of Low Dimensional Materials and Technology, College of Science, Civil Aviation University of China, Tianfin 300300, China;Sino-European Institute of Aviation Engineering, Civil Aviation University of China, Tianjin 300300, China)

机构地区：[1]中国民航大学理学院低维材料与技术研究所,天津300300 [2]中国民航大学中欧航空工程师学院,天津300300

出　　处：《稀有金属》2018年第7期705-712,共8页Chinese Journal of Rare Metals

基　　金：国家自然科学基金项目(11304380);中国民航大学中央高校基本科研业务费(3122014K001)资助

摘　　要：采用基于密度泛函理论的第一性原理方法，计算研究了影响Nb替位Ti（或Al）掺杂，且浓度为1．85％，2．78％，4．17％，6．25％（原子分数，下同）的γ-TiAl合金延性的电子性质因素。结果显示，Nb替位掺杂具有较好的能量稳定性，且不同掺杂浓度引起的晶格参量的改变不同。当Nb替代Al原子且掺杂浓度为1．85％～4．17％时，合金的轴比将会减小更接近于1，此时合金的延性改善效果明显，就所研究的晶胞模型而言，Ti12Al11Nb合金的延性最佳。故以掺杂浓度为4．17％的Ti12Al11N11和Ti11NbAl12合金为例，研究掺杂Nb改善γ-TiAl基合金延性的电子结构因素。研究结果表明：在该掺杂浓度情况下，N11替代Al原子使n4s→3d，A13s→3p的电荷转移明显减少，Alp—Tid轨道杂化作用减弱，形成金属键的自由电子数量增多，金属性增强，合金延性得到改善；Nb替代Al原子掺杂会使合金的共价性减弱，且化学键Al—Al，Ti—Ti和Al-Ti强度明显趋同，这将会显著提高γ-TiAl基合金的各向同性程度，从而使该类合金的延性得以改善。Nb-doped γ-TiAl based alloys were investigated using first principles method based on density functional theory. The crystal structure stability, ductility and electronic properties were calculated in four different impurities： 1.85%, 2.78%, 4.17% and 6. 25% （atomic fraction）. The results showed that all Nb-doped alloys got a good energy stability, which indicated those can be prepared in experiment and stable in existence. The lattice parameter changed with Nb doping concentration. When Nb substituted AI atom by 1.85%-4.17% , the axial ratio of the alloy would decrease to 1. Then the ductility of the alloy was improved obviously. The ductility of Ti12Al11 Nb alloy was the best among all super cell models. Take Ti12Al11 Nb and Ti11NbAl12 alloys that doped with 4.17% as examples, the electronic structure factors of improving the ductility of Nb-doped γ-TiAl alloys were studied. The results showed that under this doped concentration conditions, there were two electronic structure factors for the improvement of ductility. Firstly, thanks to that the transfer charge of Ti 4s→3d and Al 3s→3p decreased significantly, the p-d orbital hybridization were weakened, the number of free electron metal bond were added, metal property were strengthened, so the ductility of γ-TiAl based alloys were enhanced. Secondly, the strength difference degree among of Al - Al, Ti - Ti and Al - Ti bonds reduced significantly, which improved the isotropie degree of γ-TiAl based alloys remarkably. In summary, this change of electronic structure of γ-TiAl would improve its ductility.

关 键 词：Nb掺杂γ-TiAl 晶体结构 延性 电子性质 

分 类 号：TG146.2[一般工业技术—材料科学与工程]