增强相原位反应对碳纤维复合材料润湿及其与金属钎焊的影响机理

Carbon reinforcement composite active filler is utilized to improve the interfacial microstructure and the property of Cf-reinforced composite/metal brazed joints. TiC formed by the in-situ reaction between carbon reinforcement and the braze alloy is beneficial to the adjustment of interface structure and the stress state, resulting in the improvement of joint performance. In the present work, interfacial reaction mechanism and the corresponding product growth feature between braze alloy and grapheme, carbon nanotubes and carbon fibers are investigated in detail. The effect of reaction characteristics on the wettability of braze alloy is revealed, which will help establish kinetic equation of spreading process. According to the optimization of brazing parameters and exploring the evolution of interfacial microstructure, the reaction model of interface can be built. The influence of in-situ reaction between reinforcement and braze alloy on the interfacial structure, especially on the reaction layer growth kinetics, is clarified. The internal relation between microstructure, stress state and shear strength is revealed. Finally, the effects of carbon reinforcement on the wetting and joint strengthening can be illuminated. This research aims to expound the joint strengthening mechanism caused by carbon reinforcement from microcosmic point of view, and provides valuable theoretical reference for the application of potential carbon materials in the joining structure of composites and metal.

本项目针对碳纤维增强复合材料与金属钎焊接头界面组织与性能调控的难题，采用碳增强相复合活性钎料进行连接，通过钎焊过程中碳增强相与钎料原位生成TiC、进而调控界面结构及应力状态的方法获得性能优异的接头。重点研究石墨烯、碳纳米管和碳纤维三种增强相与钎料微观界面处的反应机制及组织择优生长取向特征；阐明其反应进程与产物分布特征对钎料在复合材料表面润湿行为的影响规律，建立复合钎料的铺展动力学方程；基于钎焊工艺参数的优化选择及界面组织演化规律的探索，构建接头界面反应模型；解明增强相与钎料的反应特征对界面结构，尤其是复合材料侧反应层生长动力学的影响规律；揭示界面结构特征及演化与接头应力状态、抗剪强度的内在关联，阐明碳增强相对钎料润湿及接头强化的影响机制。本课题旨在从微观角度阐释碳增强相在复合材料与金属钎焊接头强化中的作用机制，对石墨烯等有潜力的碳材料在复合材料与金属连接结构中应用提供有价值的理论参考。

针对陶瓷/金属与复合材料/金属异质钎焊接头界面组织与性能调控的难题，本项目从陶瓷/金属与复合材料/金属异质钎焊接头界面组织调控与应力缓解开展基础研究。传统的陶瓷/金属与复合材料/金属钎焊过程中会使得接头处存在较大的残余应力，钎缝强度不高，严重降低连接构件的承载性能和可靠新。针对上述问题，本项目提出了碳材料增强复合钎料用以缓解陶瓷/金属与复合材料/金属异质钎焊接头残余应力的新方法。通过引入低热膨胀系数的碳材料增强相（石墨烯、碳纳米管、碳纤维）形成复合钎料，实现了陶瓷/金属与复合材料/金属的可靠钎焊连接及残余应力缓解。基于复合钎料反应体系热力学和动力学分析，获得了复合钎料设计准则，研究了复合钎料中碳增强相与钎料微观界面反应产物的生长取向特征，阐明了碳增强相与钎料界面反应对钎料润湿性的影响规律，研究了母材与复合钎料相互作用的溶解扩散方程及复合钎缝组织演化过程；解明了复合钎料钎焊陶瓷/金属与复合材料/金属异质材料的反应机理；基于接头强化机理的解析（细晶强化、位错强化及Orowan强化），解明了接头强度提升的原因；结合钎焊接头残余应力计算模拟分析，揭示了复合钎料对接头残余应力的缓解机制及对性能的调节改善作用机理。本项目顺利完成了研究计划所规定的各项研究内容，达到了预期的研究目标，取得了丰富而显著的研究成果。截至目前，项目组人员参加国内外学术会议2人次，培养博士生2名，硕士生7名，发表论文共计20篇，其中SCI检索论文18篇，EI论文2篇；申请国家发明专利11项，其中已授权7项。