Ti3AlC2/TiAl基复合材料的制备、微结构调控与性能研究

As the new light-weight high-temperature structural material, TiAl intermetallic compounds have great potential application in aerospace engine, energy and automotive fields. But the bottleneck problems including poor room temperature ductility and high-temperature oxidation resistance limit their application. Layered ternary carbide Ti3AlC2 which combines many of the merits of both metals and ceramics, is the best reinforcement for TiAl intermetallic compound. In this project, the key scientific problems of reinforcement dispersion and interface combination which restrict the realizing of composite effect during the preparation process of Ti3AlC2/TiAl matrix composites are investigated. The design criterion of composite interface is established. The interacting between Ti3AlC2 reinforcement and matrix, and the formation mechanism of composite interface are revealed, so as to realize the effective control of composite interface and structure. By studying on the relationship of the processes, microstructure and properties of the composites, the coupling rule of composite structure and mechanical behavior are demonstrated, and the strengthening-toughening mechanism is discussed. By the high-temperature oxidation experiments, the high-temperature oxidation rule and the main influencing factors are analyzed, the high-temperature oxidation dynamic model is estabilished, and the high-temperature oxidation mechanism is discussed. This research will make TiAl matrix composites lighter, stiffer, stronger and more thermoduric, so as to better meet the demand of economy and social development for light-weight high-temperature structural materials.

TiAl金属间化合物是一种在航空航天发动机、能源及汽车工业领域中极具应用潜力的轻质高温结构材料，但是本征脆性以及高温氧化抗力不足等瓶颈问题亟需解决。柔性Ti3AlC2三元层状化合物兼具金属-陶瓷的双重特性，是TiAl金属间化合物最为理想的增强相之一。本项目通过研究Ti3AlC2/TiAl基复合材料制备过程中增强相分散、界面结合等制约复合效应发挥的关键科学问题，建立复合界面设计准则，揭示增强相与基体之间的作用以及复合界面形成机制，实现复合界面及结构的有效调控；系统研究工艺-结构-性能之间的关系，探讨强韧化机理，揭示微结构与力学行为的耦合规律；通过高温氧化实验，分析高温氧化行为以及主要的影响因素，建立高温氧化动力学模型，揭示高温氧化机制。本项目研究有望使TiAl基复合材料"更轻、更刚、更强和更耐热"，从而更好地满足国家经济和社会发展对轻质高温材料的需求。

Ti-Al系金属间化合物是一类在航空航天、汽车工业等领域极具应用潜力的轻质耐高温结构材料，但是室温脆性大以及超过800℃氧化抗力不足等技术难题仍需解决。复合化技术是改善Ti-Al系金属间化合物性能缺陷的有效方法。MAX化合物（典型化合物Ti3AlC2和Ti2AlC）同时兼具金属和陶瓷的优良性能，热膨胀系数与Ti-Al系化合物接近，被认为是其理想的增强相。.本项目在Ti-1.2Al-2TiC体系中掺杂不同含量的Si或Sn，成功解决了高纯Ti3AlC2制备技术难题，利用2TiC-Ti-1.2Al-0.05Sn-0.1Si体系制备的Ti3AlC2纯度高达98.94wt%，并探讨了Si、Sn对合成高纯Ti3AlC2的协同作用机制。将高纯Ti3AlC2粉与Ti/Al混合粉或Ti-Al预合成粉混合以及设计Ti-Al-TiC-CNTs体系，开展了内生Ti2AlC/Ti3AlC2/Ti3AlC2-Ti2AlC颗粒增强TiAl或TiAl3金属间化合物研究，系统研究了不同种类、数量及组合方式的内生Ti2AlC/Ti3AlC2/Ti3AlC2-Ti2AlC颗粒对TiAl或TiAl3金属间化合物微观结构和力学性能的影响规律，构建了工艺-组成-结构-性能之间的关系，实现了从制备和微结构调控入手增强宏观力学性能。深入研究了MAX相对Ti-Al系金属间化合物的作用机理。分析了第二相强化、晶界强化和细晶强化对强度的贡献作用；裂纹扩展SEM照片分析表明柔性第二相增韧、穿晶断裂、层间撕裂以及裂纹偏转、桥联和分叉等混合断裂特征对改善韧性发挥了重要作用，并提出进一步改善Ti-Al系金属间化合物室温力学性能的途径。900℃（空气）恒温氧化实验表明，通过MAX相增强Ti-Al系金属间化合物具有良好的抗高温氧化性能，其氧化基本遵循抛物线规律，分析了氧化表面形貌及氧化层结构，探讨了MAX相对高温氧化性能的作用机理。本项目为Ti-Al基金属间化合物的进一步性能优化、工程化制备及其实际应用研究提供了丰富的实验数据和技术支撑。