纳米多层膜钎料熔点降低的尺寸效应和界面反应机理研究

传统钎料因其液相线温度接近或高于母材固相线温度导致接头强度和钎缝成形性下降，难以满足具有温度敏感特性的先进金属合金可钎焊性的要求，对能够降低钎焊温度的新型钎料和连接技术提出了新的挑战。本项目基于尺寸效应降低纳米结构材料熔点的原理，提出采用纳米多层膜钎料进行温度敏感合金的钎焊。从界面结构设计和制备工艺入手，研究纳米钎料层和扩散阻隔层的成分和厚度对熔点降低的影响，结合微观结构表征结果，搞清纳米多层膜钎料熔点降低的尺寸效应及微观机理；采用纳米量热技术研究纳米多层膜钎料的熔化和凝固特性，获得具有熔点降低性能的纳米结构的临界尺寸；对纳米多层膜钎料钎焊接头的力学性能进行电学表征，研究界面微观组织演变行为对接头综合性能的影响研究，从而对纳米多层膜结构进行原位调控并阐述其连接机理。本项目将为研究纳米多层膜钎料熔化和凝固的基础科学问题提供新的思路，对于降低温度敏感材料的连接温度和提高接头可靠性具有重要意义

As the liquidus temperature of traditional brazing filler metal alloys approaches the solidus temperature of the base material or is high enough to cause its microstructural changes and finally affect the joint strength and performance of fillet, thus it cannot meet the requirement for the braze-ability of temperature sensitive advanced metallic alloys, which puts forward the new challenge for the new brazing filler metals with melting-point depression (MPD) effect and new brazing technology. Based on the principals of size effect on the melting-point depression of nanoscale materials, the project proposed to develop a new nano multilayer film filler to be utilized to braze temperature sensitive alloys. The research starts from interfacial structural design and preparation of nano multilayer film filler. The effect of deposition and thickness of nano filler metal layer and diffusion barrier layer on the decreasing of melting point will be studied. Combined microstructure characterization, the size effect on melting point depression of nano multilayer film and the microscopic mechanism is to be understood. In addition, the melting and solidification behavior of nano multilayer film filler will be studied using nanocalorimetry method so as to obtain the critical dimensions of nano structure with MPD effect. The electrical characterization of mechanical properties of the joint brazed with nano multilayer film filler will be performed. What's more, the interfacial reaction, the microstructure evolution and its effect on the performance brazed joint will be studied to apply in-situ control of nano multilayer structure as well as declare the bonding mechanism. The project aims to open novel mind for studying fundamental scientific questions in melting and solidification of nano multilayer film filler, which is of significance to reduce the brazing temperature of temperature sensitive alloys and improve joint quality.