C/C复合材料与Ti3Al基合金TLP扩散连接多界面设计、组织结构演变及应力缓解机理研究

Both carbon/carbon (C/C) composites and Ti3Al based alloy are advanced high temperature structural materials in aerospace and aviation due to their unique properties such as low density, high specific strength, excellent resistance to thermal shock, in which joining technique is one of the key for their engineering applications. The scientific issues on the joining of C/C composites and Ti3Al based alloy mainly include the interface design, joining mechanism and stress alleviation of joint. In this program, combined with surface modifying of C/C composites, using multiple interlayers as joining materials, gradient structural C/C composites/Ti3Al based alloy joints are prepared by transient liquid phase (TLP) diffusion bonding technique. According to the microstructural characterization and phase analysis in the joining region, the diffusion, reaction and evolution of interface are investigated. Furthermore, reasonable TLP diffusion bonding mechanism can be proposed and the relations between microstructure and mechanical properties of joint can be explored. Meanwhile, a finite element (FE) model is used to simulate the stress distribution in C/C composites/Ti3Al based alloy joint, in which the effects of gradient microstructure and coefficience of thermal expansion on the residual stress distribution in joints are primarily investigated. Comparing the simulated results and experimental tests, FE model can be modified and improved to optimize the joining process and reasonable mechanism of stress alleviation may be proposed.

炭/炭(C/C)复合材料和Ti3Al基合金均为轻质高强的高温结构材料，是高推比发动机、先进飞行器的重要组成部分，在航空航天等领域中具有广阔的发展前景，而二者的连接技术是拓展其工程应用的关键之一。作为异种材料，C/C复合材料与Ti3Al基合金的连接主要涉及的科学问题有：界面设计、连接机理及应力缓解机理。本项目设计复合中间层体系，结合C/C复合材料表面改性处理，采用瞬间液相(TLP)扩散连接方法制备出具有梯度结构的C/C复合材料/Ti3Al基合金接头。在此基础上，通过对连接区域微观结构和物相组成进行分析表征，研究界面的扩散、反应和演变，提出合理的连接机理，并探讨连接区域微观结构与接头性能的关系；同时，采用有限元方法建立接头应力分布模型，并进行计算模拟，研究梯度结构中间层和热膨胀系数等对接头残余应力分布的影响，并与实验测试结果对比分析，进一步优化连接工艺，提出合理的界面优化设计和应力缓解机理。

作为两种轻质、高强的高温结构材料， 炭/炭（C/C）复合材料和Ti3Al基合金在航空航天等领域中发展前景广阔，而通过连接技术制备C/C复合材料/Ti3Al基合金复合构件是拓展其工程应用的有效途径之一。基于两种材料的物化性能，本项目设计了Ti/Ni/Ti/Ni、Ti/Ni/Nb、AgCuNiLi等多种中间层体系，采用瞬间液相（TLP）扩散连接技术制备了具有梯度结构的C/C复合材料/Ti3Al基合金接头，研究了连接区域的界面扩散、反应和演变，提出了合理的连接机理，揭示了微观结构与接头性能的关系。在此基础上，分别在C/C复合材料表面磁控溅射Cr涂层和化学气相沉积SiC晶须涂层进行表面改性，并将表面改性后的C/C复合材料和Ti3Al基合金进行TLP扩散连接实验和分析表征，阐明了C/C复合材料表面改性对连接过程的影响，探索了合理的应力缓解途径，获得了优化的连接工艺。发表标注论文10篇，其中SCI收录8篇，申请国家发明专利1项。本项目研究有助于强化异种材料TLP扩散连接界面和结构设计的观念，加深对连接过程中界面演变和应力缓解的认识，可为相关材料连接工艺的优化提供参考和借鉴依据。