基于急冷活性钎料的W-Cu复合材料与不锈钢钎焊机理及热疲劳失效研究

W-Cu composites has considerable merits of thermal, electric conducting and dimensional stability, widely been used in manufacturing components that need to withstand high temperature and corrosion for power electronic, aerospace and wepon industries. Usually, only a part of the component will need to withstand the specific load, temperature or effect of corrosive media, so connecting W-Cu composites and other materials to form a composite structure will make full use of their respective performance advantages. While W-Cu composites and stainless steel being brazed,microstructure deteriorated by thermal recycle and weld failure induced by contamination of gas impurity and stress concentration were the key to affect quality of the obatined joint. In this project, rapidly quenched active brazing foils are adopted to brazing W-Cu composites and stainless steel. First, the alloy system of being used to braze W-Cu composites is designed and alloy constituent is optimized. The brazing alloy is based on Ni(Fe)-Si-B alloy and contained active elements (Ti、Zr、Cr and so on). And the influence of component and morphology of brazing alloy on the phase structure, distribution morphology and micostructure stability are investigated. The metallurgy on interface of brazing seam and initiation and expand mechanism of thermal fatigue cracks is revealed.Then, mechanism of controlling microstructure, failure of thermal fatigue and strength mechanism are clarified theoretically. Finally, a quantitative and qualitative method is estabilished to evaluate the reliability of the joint of W-Cu composites and stainless steel under thermal recycle. This study is based on current situation of joining W-Cu composites and stainless steel, therefore this project has important theoretical significance and practical value to promote development of complicated components of W-Cu composites and application as high temperature materials on manufacture of hot end components in power electronic, aerospace and wepon industries.

W-Cu复合材料具有良好导热、导电性和尺寸稳定性，被广泛应用于能源、电子、航天及武器装备等领域。W-Cu复合材料与不锈钢钎焊连接时，接头组织结构稳定性和由气体杂质污染及焊接应力引起的焊缝性能失效是影响接头质量的关键。本项目提出采用急冷活性钎料钎焊连接W-Cu复合材料与不锈钢，研究Ni(Fe)-Si-B合金添加活性元素（Ti、Zr、Cr等）的多元系急冷活性钎料设计，钎料成分及形态对合金相结构、形态分布及组织稳定性的影响，钎缝界面冶金反应及热疲劳裂纹萌生、扩展机制，揭示W-Cu复合材料与不锈钢钎缝组织控制及热疲劳失效和强化机制，建立W-Cu复合材料与不锈钢钎焊接头在循环热载荷作用下的定量和定性评价方法。该研究对促进W-Cu复合构件在电力电子器件、航天及军用装备热端部件制造领域推广应用具有重要理论意义和工程实用价值。

依据研究计划，本项目采用急冷活性钎焊方法对W-Cu复合材料与不锈钢连接机理及其热疲劳损伤机制等基础问题进行了研究。设计优化了新型Ni基急冷活性钎料，系统研究了新型钎料在W-Cu复合材料表面的润湿特性、熔化特性及结构形态。掌握了成功实现W-Cu复合材料与不锈钢高强可靠连接的工艺范围。并对W-Cu复合材料与不锈钢钎焊连接界面冶金反应机理等进行研究，阐明了W-Cu异种材料接头界面组织结构形成与演变规律，连接强度的影响因素与接头断裂机制。在此基础上进一步研究了W-Cu复合材料异种接头的热疲劳裂纹萌生、扩展及导致界面失效的机制，建立了W-Cu复合材料接头热疲劳失效机理模型，确定了钎料组元-钎焊工艺-界面强度-热疲劳失效的内在联系。本项目已发表（含待出版）论文11篇，申请国家发明专利11项（其中已授权6项），申请并获授权实用新型专利3项。本项目阐明了W-Cu复合材料连接及其热疲劳性能的基础理论，形成了相关关键技术，为实现W-Cu复合材料及类似材料的可靠连接，推动其复合构件的应用提供了基础理论与关键技术支持。