Ti2AlC陶瓷与金属连接过程中陶瓷稳定性和钎焊机理研究

Using Ag, Al, Ag-Cu, Al-Si and Cu-Ti alloys as filling materials, Ti2AlC and metals (Ti, Cu, Ni) are bonded by brazing technique. Effects of brazing environment, composition of the filling materials, types of bonded metal, braze bonding parameters on microstructure characteristic of the joint and phase stability of the Ti2AlC ceramic are investigated by means of experiments and theoretical calculation. Relationships between microstructure evolution of Ti2AlC ceramic and joint and mechanical properties, electric conductivity and oxidation resistance of the joint are analyzed. The formation of Al vacancy in the Ti2AlC ceramic and its interaction with Ag, Al, Cu, Si, Ti, Ni elements are discussed in theory. Based on the successful bonding btween Ti2AlC and metals, structure stability and typical properties of the Ti2AlC ceramic are kept, and braze bonding mechanism is studied. This research will provide the theoretical basis for the brazing technique btween Ti2AlC and metals, composition design of filling material, optimization of joint microstructure, obtaining the joint btweeen Ti2AlC and metals with high stability of structure and properties, and also contribute to the basic theory of structure stability of the Ti-Al-C ceramics.

采用Ag、Al、Ag-Cu、Al-Si、Cu-Ti作为钎料，通过钎焊方法连接Ti2AlC陶瓷与金属（钛、铜、镍）。利用试验和理论计算的方法系统研究钎焊环境、钎料组元的构成及成分、被连接金属的种类、连接工艺参数对接头组织特征和Ti2AlC陶瓷结构稳定性的影响。分析陶瓷母材和接头中的微观组织演化与接头的力学性能、导电性能和抗氧化性能之间的关系。从理论上阐述Ti2AlC陶瓷中Al空缺的形成与Ag、Al、Cu、Si、Ti、Ni等不同金属元素之间的交互作用原理，探求既实现Ti2AlC陶瓷本身及其与金属的成功连接，又保持陶瓷母材的结构稳定性，并发挥其独特性能的途径，揭示钎焊连接机理。为指导Ti2AlC陶瓷与金属的连接工艺、钎料成分设计、接头微观组织优化、获得组织和性能稳定的Ti2AlC陶瓷与金属的接头奠定理论基础，并丰富Ti-Al-C陶瓷结构稳定性研究的基础理论。

Ti2AlC陶瓷是一种兼具陶瓷与金属的性能的新型材料，在电极材料、自润滑材料和原子能反应堆覆层材料等应用领域具有广阔的应用前景。本研究分别采用Ag基(Ag,Ag-Cu)、Al基(Al,Al-Si)、Ni基钎料连接Ti2AlC陶瓷，以及Ti2AlC与金属Cu、Ni的连接，研究了钎料成分和钎焊工艺参数对接头微观组织、力学性能和导电性能的影响规律，获得了最佳钎焊工艺参数与最佳接头性能。利用钎焊，创造一种特殊的液态金属与Ti2AlC陶瓷的交互作用条件，采用第一性原理，计算了液态钎料与陶瓷母材的交互作用，以及钎料元素中的原子对Ti2AlC陶瓷母材中原子的取代现象，利用高分辨透射电子显微镜对原子取代现象进行了验证，揭示了Ti2AlC陶瓷的结构稳定性与液态钎料种类和含量的关系。结合第一性原理计算和TEM观察，首次从原子尺度阐明并验证了Si、Ag元素对Ti2AlC陶瓷中的原子取代作用。使用BNi-2钎料连接Ti2AlC陶瓷，获得了剪切强度达到母材强度90%的接头。阐明了不同液态金属与Ti2AlC陶瓷的交互作用机制，为这种陶瓷材料的设计、制备和使用条件下的稳定性评价提供了理论依据。