CAJ | 학술논문

现代高分辨电镜和高空间分辨分析电镜,使我们可以在纳米和原子尺度研究材料的显微结构和微区成份,从而极大地加深了我们对材料的结构与性能的理解.另一方面,随着信息技术的飞速发展,计算材料学也以前所未有的广度和深度,冲击着材料研究的模式.对显微结构的研究也是如此.材料的微结构,作为组成材料的大量原子在空间中的排列,本质上是由原子间的相互作用,即化学键决定的.借助第一原理总能与电子结构计算可给出原子间成键的详尽的信息,它在显微结构及其演变的研究中有很好的应用前景.本论文将先进电子显微术与计算材料学有机地结合起来,在从纳米、原子尺度到电子尺度等多个层次对钛基金属间化合物和陶瓷(Ti3SiC2,TiC,TiAl)的结构进行了研究.
현대고분변전경화고공간분변분석전경,사아문가이재납미화원자척도연구재료적현미결구화미구성빈,종이겁대지가심료아문대재료적결구여성능적리해.령일방면,수착신식기술적비속발전,계산재료학야이전소미유적엄도화심도,충격착재료연구적모식.대현미결구적연구야시여차.재료적미결구,작위조성재료적대량원자재공간중적배렬,본질상시유원자간적상호작용,즉화학건결정적.차조제일원리총능여전자결구계산가급출원자간성건적상진적신식,타재현미결구급기연변적연구중유흔호적응용전경.본논문장선진전자현미술여계산재료학유궤지결합기래,재종납미、원자척도도전자척도등다개층차대태기금속간화합물화도자(Ti3SiC2,TiC,TiAl)적결구진행료연구.
Transmission electron microscopy and first-principles calculations are integrated to investigate the crystal structures and the microstructures of titanium-based intermetallics and ceramics on the nanometer, atomic, and electronic scales. The thesis contains three parts.(1) Distribution of W and the precipitation mechanism of the B2 phase in the lamellar structure of a TiAl alloy. The B2-stabilizing effect of W and its site preference can be explained well on the basis of the pseudo-gap effect and the strong covalent W Ti bonding. (2) The polymorphism, electronic structure, and microstructure of Ti3 SiC2. Unconventional stacking faults have been identified, which result from insertion of additional TiC layers into normal Ti3 SiC2 crystal, instead of from the dissociation of dislocations which occurs in most materials. (3) The effect of alloying elements Si and Al on the twin boundary energy of TiC. It was found that Si and Al can reduce the twin boundary energy of TiC, leading to the formation of a lot of microtwins.