【作者】 林哲；

【导师】 谭毅；

【作者基本信息】 大连理工大学 ， 材料学， 2007， 硕士

【摘要】 TiAl基金属间化合物被认为是最有应用潜力的新一代高温结构材料，其中高铌TiAl基合金代表着高温高性能TiAl基合金的最新发展方向，也最具有实际应用前景。但从目前研究来看，单纯的金属间化合物无法满足一些特殊的航空部件对高温强度、蠕变抗力和持久性能的综合要求，而制备成金属间化合物基复合材料可能获得良好的力学性能，同时还保持各组分优点。本文研究者使用熔炼法和热压烧结法制备了一系列具有不同成份和配比的高铌TiAl基金属间化合物，并以此为基体制备了金属间化合物基复合材料。研究了熔炼法制备的高铌TiAl基金属间化合物在不同温度下的力学性能，同时用氧化增重法研究了高铌TiAl基复合材料在静止空气中1000℃／100h的间断氧化行为。综合使用X-射线衍射仪（XRD）、配有能谱仪（EDS）的扫描电子显微镜（SEM）、电子探针显微分析（EPMA）等实验手段，研究了所熔炼和热压烧结的高铌TiAl基复合材料的相组成以及高温下形成氧化膜的表面及剖面的组织特征。研究结果如下：1．在等原子比的TiAl基金属间化合物的基础上添加不同量的铌元素，用熔炼法获得了三种含不同组成相和微观组织的合金Ti-47.5Al-5Nb、Ti-42.85Al-14.3Nb和Ti-40Al-20Nb（at％）。力学性能实验结果表明，由γ-TiAl相和α₂-Ti₃Al相构成的合金Ti-42.85Al-14.3Nb为层片状组织，在从室温到1200K的压缩试验中具有较高的屈服强度，在1373K的拉伸试验中发生韧性断裂。2．用熔炼法制备了以ZrC颗粒为增强相以Ti-47.5Al-5Nb、Ti-42.85Al-14.3Nb、Ti-40Al-20Nb和Ti-30Al-40Nb为基体的TiAl金属间化合物基复合材料。高温氧化实验结果表明，增强相ZrC颗粒没有改变基体材料的氧化机制，并且由于其高温稳定性好没有和基体发生界面发应，但ZrC的加入使材料表面具有很多有利于氧向内扩散的通道，降低了材料的抗氧化性，本实验中的几种TiAl金属间化合物基复合材料的高温抗氧化性普遍低于基体材料。3．用热压烧结法制备了两种金属间化合物：Ti-47.5Al-5Nb和Ti-42.85Al-14.3Nb，并加入SiC晶须为增强相制成复合材料。高温氧化实验结果表明，SiC晶须的加入有利与TiAl金属间化合物表面形成致密的Al₂O₃层，提高了材料的抗氧化性。更多还原

【Abstract】 The TiAl intermetallic compound is an attractive material for high-temperature structuralapplications. High-Nb TiAl based alloy represents the latest trend of the development of TiAlintemetallic compound. From recent studies, the simplex intermetallic composite has notmany kinds of properties such as good high temperature strength, good creep resistance orexcellent endurant property at the same time. However, if these intermetallic compounds areenforeced by particles or whiskers to be composites, they will have not only their ownproperties, but also excellent synthetical properties. In this paper, a series of High-NbTiAl-based alloys and their composites were made by smelting or hot pressing sintering. Thentheir mechanical properties and oxidation resistance at 900℃or 1000℃/100h in air werestudied. The phase composition of the alloys and the character of the oxidation at hightemperature were analyzed by XRD、SEM （equipped with EDS） and EPMA.Based on the researches above, the conclusions of this paper are as follows:1. Three alloys with different microstructure were made using smelting method by addingdifferent amount of Nb into TiAl alloys, that was Ti-47.5Al-5Nb, Ti-42.85Al-14.3Nb andTi-40Al-20Nb （at%）. From mechanical properties test, it’s seen that Ti-42.85Al-14.3Nb withsandwich structure is made up ofγ-TiAl andα₂-Ti₃Al, and it has higher yield strength incompressive test, and high ductile fractures at 1373K in tensile property test.2. ZrC particles reinforced Ti-47.5Al-5Nb、Ti-42.85Al-14.3Nb、Ti-40Al-20Nb andTi-30Al-40Nb based composites were made by smelting. The results of oxidation at hightemperature are as follows: ZrC particles don’t change the oxidation mechanism of thematrix. And because of the good high-temperature stability, no interface reactions occur. Butaddition of the ZrC makes the surface having many channels good to oxidation diffusion andreduces the oxidation resistance. The oxidation resistance of the TiAl-based intermetalliccomposites is generally worse than their parent material.3. Ti-47.5Al-5Nb and Ti-42.85Al-14.3Nb were made by hot pressing sintering. SiCwhiskers reinforced Ti-47.5Al-5Nb and Ti-42.85Al-14.3Nb were also made by the same way.High temperature oxidation test tells, SiC whisker is good for Al₂O₃ forming at the surfaceand improves the oxidation resistance of the TiAl alloys.更多还原