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

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.

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

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，难以满足温度敏感材料对连接的要求。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（NML）作为中间层钎料进行温度敏感材料的连接。对两种不互溶体系Ag-Cu/W和Cu/W纳米多层膜进行了界面设计，通过磁控溅射工艺参数优化，制备了成分、厚度和结构可控的纳米多层膜。研究了纳米钎料层和扩散阻隔层的调制比对多层膜熔点降低的影响，Cu/W体系熔点降低约100°C，Ag-Cu/W体系熔点降低约170°C。系统研究了纳米多层膜钎料的热力学熔化特性和动态润湿性，建立了熔化的热力学模型。深入研究了不同退火温度下Cu/W纳米多层膜微观结构的演化规律，搞清了钎料熔点降低的尺寸效应及微结构热稳定性。应用纳米多层膜作为钎料，对同种304不锈钢、不锈钢与Ti6Al4V钛合金进行真空钎焊，研究了温度、压力和薄膜沉积层数等工艺参数对接头组织和性能的影响，同种304不锈钢钎焊接头最大抗剪切强度达181.1MPa，并对钎焊接头的力学性能进行了电学表征，研究了界面微观组织演变行为对接头综合性能的影响。.此外，基于真空或大气环境下微电子芯片、金属与非金属等低温连接的需求，项目以反应性纳米多层膜（RNML）作为中间层，开展了Ti/Ni、Ni/Al和Ti/Si纳米多层膜的连接研究。制备并获得了调制结构与热学性能相匹配的纳米多层膜，分析了薄膜在低能量诱发条件下反应的放热过程、反应波传播速度和反应产物。并对Ti/Ni薄膜自蔓延放热反应过程的界面扩散进行了分子动力学模拟，研究了原子比、加热温度以及空位对界面原子互扩散行为的影响。采用Ti/Ni纳米多层膜作为中间层辅助Ti6Al4V合金真空瞬时液相扩散连接，研究了原子比和压力、温度等对接头组织和性能的影响，分析了界面反应和接头失效机理；研究了Ni/Al多层膜自蔓延反应连接碳纤维增强塑料（CFRP）和铝合金，获得了薄膜厚度和压力对接头强度的影响规律；并探讨了Ti/Si纳米多层膜应用于自蔓延反应连接碳泡沫的可行性。.项目系统研究了纳米多层膜钎料的熔化和退火过程的微结构演变规律等基础科学问题，为面向微纳器件制造、互连焊接、3D叠层封装、航空航天和水下焊接等领域温度敏感材料的连接提供了理论研究基础，对降低连接过程对外加热源的要求，精确控制母材热输入，提高接头的可靠性具有重要工程应用价值。