TiAl金属间化合物力学性质及韧化机制的计算研究.doc

TiAl金属间化合物力学性质及韧化机制的计算研究 The Calculation of Mechanical Properties and Toughening Mechanisms of TiAl Intermetallic Compounds 摘 要 Kim [8 ]认为, 同时加入N b和Cr对提高TiAl合金性能最为有效。本论文选择TiAl作为研究对象，以TiAl合金化的部分实验结果为依托背景，采用第一原理的研究方法，主要研究3d过渡元素对TiAl金属间化合物力学性质的影响来揭示TiAl的韧化机制。 本论文计算了富Ti和富Al的TiAl体系的平衡晶格常数、合金形成热、电子态密度、能带等，并与他人的计算值和实验值比较，发现都比较接近。从合金形成热和电子态密度发现富Al状态的TiAl合金形成热最小，以判断其最稳定。在这个基础上，对富Al的TiAl合金添加3d过渡元素（Zn、Co、Fe、Sc、Nb、V、Cu、Cr），从弹性模量的角度分析合金化后对TiAl力学性质的影响。 合金化后分别计算了8种元素分别替代TiAl的中心Al原子的总能量、合金形成热、电子态密度、弹性常数（与他人和实验值相比），对以上数据先分析了合金化后与合金化前的稳定性，而后计算了8种元素替代Al原子之后的弹性常数，通过杨氏模量E、剪切模量G及其与体模量B的比值G/B和泊松比(。等来分析对TiAl合金的影响，从硬度、韧性和原子平均价键等方面得出改善TiAl金属间化合物脆性的元素。得出的结论是Fe、Cr、Co合金化后都提高了TiAl的延性，从电子云的角度分析SclZnVFeCuNbCrCoTiAl，从不同的角度分析，结果略有所改变。 关键词：；合金形成热；；第一性原理计算 Abstract With the development of the aerospace, aviation, atomic energy and others, people make higher and higher requests on the properties of materials ,especially the new structural materials in the development and application of intermetallic compounds . In the Ti-Al based metal compounds, TiAl based alloy have many advantages, such as ,small density, strong high- temperature properties and so on, which is very popular and has great potential in the supersonic speed and loud aircraft .But it exists some disadvantages in terms of brittleness and thermal stability. At present, people are trying to improve its brittle greenhouse by alloying and thermal processing. Many researchers have experimented with some elements of the alloy. In Kim’s opinion [8],it is the most effective way for the growth of the performance of TiAl alloy to add Nb and Cr simultaneously. In the paper, TiAl as the research object ,and part result of TiAl alloys as the background, we main study 3d transition elements acting on TiAl intermetallic compound to reveal the toughening mechanism of TiAl by using the first principles of research methods, In the paper, we calculate quilibrium lattice constant, formation heat, electronic density of states, band in the Ti-rich TiAl and A