基于密度泛函理论的La掺杂γ-TiAl体系结构延性与电子性质

发布时间：2017-12-31 23:13

本文关键词：基于密度泛函理论的La掺杂γ-TiAl体系结构延性与电子性质　出处：《物理学报》2017年06期 　论文类型：期刊论文

更多相关文章： La掺杂γ-TiAl 晶体结构 延性 电子性质

【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La替位Ti或Al且掺杂浓度分别为1.85 at.%,2.78 at.%,4.17 at.%,6.25 at.%,8.33 at.%,12.5 at.%的γ-Ti Al合金的晶体结构、稳定性和延性等性质.结果显示,杂质La浓度x 12.5 at.%,各个体系均具有较好的能量稳定性,即在一定条件下它们是可以实验制备的,且掺杂合金体系的密度4.6 g·cm~(-3).La掺杂引起晶格参量变化进而导致合金体系的轴比发生变化.La的低浓度(x 6.25 at.%)掺杂使合金体系的轴比相较纯γ-Ti Al更接近于1,这对于改善材料的延性极为有利,其中Ti_(11)La Al_(12)体系的轴比最接近于1,预报其延性最佳.通过对比Ti_(11)LaAl_(12)和Ti_(12)Al_(12)体系的布居数、电荷密度和电子态密度,发现Ti_(11)LaAl_(12)体系延性改善的电子因素为:掺杂使体系内Al(Ti)原子轨道上的电子重新分布,Ti-d轨道和Al-p轨道的电子数均减小,可被p-d杂化轨道局域化的电子数减小,p-d轨道杂化键强度降低,从而使位错移动的阻力减少,延性得以明显改善.电子重新分布改变了部分化学键的性质,部分Al—Ti共价键转化为Al—La离子键,部分Ti—Ti共价键转化为Ti—La金属键,它们的共价性及方向性明显降低,材料金属性增强.在掺杂体系中Al—Al键的平均强度减弱,Al—Ti键和Ti—Ti键的平均强度增强,三者的强度差异明显减小,晶体结构的各向异性程度降低.
[Abstract]:The first principle method based on density functional theory is used to calculate and study La substitution Ti or Al with doping concentration of 1.85 at.0.78 at.%. 4.17 at 6.25 at.and 8.33 at.and 12.5 at.% of 纬 -TiAl alloy. The results show that the crystal structure, stability and ductility of 纬 -TiAl alloy are stable and ductile. The impurity La concentration x 12.5 at., each system has good energy stability, that is, they can be prepared experimentally under certain conditions. The density of doping alloy system is 4. 6 g 路cm~(-3).La doping, which leads to the change of lattice parameters, which leads to the change of axial ratio of alloy system. The axis of the alloy system is more similar to that of pure 纬 -Ti Al than that of pure 纬 -Ti Al. This is very beneficial to improve the ductility of the material, in which the axial ratio of Ti_(11)La Als12) system is the closest to 1. By comparing the population density, charge density and electronic density of state of tititiao 11LaAlAlC12) and Titip 12AlAlC12) system, its ductility is predicted to be the best. It is found that the electronic factor for the improvement of ductility of titii _ (11) La _ Al _ S _ 12) system is that doping causes the redistribution of electrons on the Al _ (Ti) atomic orbitals in the system. The number of electrons in both Ti-d and Al-p orbitals is reduced, and the intensity of hybrid bond is reduced by the number of localized electrons in p-d hybrid orbitals, thus reducing the resistance of dislocation movement. The ductility was improved obviously. The redistribution of electrons changed the properties of some chemical bonds, and some of the Al-Ti covalent bonds were converted into Al-La ionic bonds. Some Ti-Ti covalent bonds were transformed into Ti-La metal bonds, their covalence and directivity were obviously decreased, and the metallic properties of the materials were enhanced. The average strength of Al-Al bonds in doped system was weakened. The average strength of Al-Ti bond and Ti-Ti bond is enhanced, the difference of strength between the three bond and the anisotropy of crystal structure is decreased obviously.
【作者单位】：中国民航大学理学院低维材料与技术研究所;中国民航大学中欧航空工程师学院;
【基金】：国家自然科学基金(批准号:11304380) 中央高校基本科研业务费专项资金(批准号:3122014K001)资助的课题~~
【分类号】：O469
【正文快照】： 添加合金元素是改善该类合金延性的有效途径之1引言一[14,15],例如,添加V,Cr,Mn和Nb等均可改善双相Ti Al合金的延性.最近,通过掺杂稀土元素来Ti Al合金因具有高比强度、较好的抗氧化性和改善金属间化合物延性的方法也引起了人们的关抗蠕变性能以及低密度而成为航空航天、汽车

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