钛合金高强韧接头用新型钛基非晶钎料及连接机理研究

Titanium alloys have extensive applications in the field of aerospace, and Ti-based brazing filler metals (BFMs) are widely used for the brazing of titanium alloys. However, high contents of Cu and Ni elements in the Ti-based BFMs result in the brittleness of the brazed joints of titanium alloys. Compared with crystalline BFMs, amorphous BFMs exhibit desirable advantages including easy fabrication into a thin continuous ribbon form and homogeneity in composition and structure, etc. Therefore, design and investigation of novel amorphous BFMs for the brazed joints with high strength and toughness is the key issue for improving the security and reliability of brazed titanium alloy parts and assemblies. Moreover, limited work has been done for understanding the correlation of wetting behavior and joining mechanism with the homogeneity in structure and composition of amorphous BFMs. In this project, considering the demands for amorphous BFMs suitable for obtaining titanium alloy brazed joints with high strength and toughness, the design, formation, brazing properties and joining mechanism of novel high-performance multicomponent Ti-based amorphous BFMs with low Cu and Ni contents will be systematically studied. The wetting characteristics of the amorphous BFMs, diffusion of elements and interface reactions during the brazing process will be investigated, and their correlation with the compositions and amorphous structure of the novel amorphous BFMs will be clarified. The influence of the amorphous BFMs on the microstructure and mechanical properties of the joints and the corresponding mechanism will also be illuminated. This proposed project, which will contribute to the enrichment of fundamentals of amorphous BFMs, extension of the engineering applications of amorphous alloys, and improvement of the security and reliability of brazed titanium alloy parts and assemblies, is of great scientific and engineering significances.

钛合金广泛应用于航空航天领域，其钎焊连接多采用钛基钎料，但现有钛基钎料中Cu和Ni含量高而导致钎焊接头存在很大脆性。与晶态钎料相比，非晶合金钎料具有成带性好、成分和结构均匀等优点。因此，设计和研究钛合金高强韧钎焊连接用新型钛基非晶钎料是提高钛合金钎焊构件安全可靠性所面临的关键问题。同时，关于非晶合金钎料的润湿行为和连接机理与其非晶结构及成分的关联也缺乏系统深入研究。本项目拟针对钛合金高强韧钎焊接头用非晶钎料的需求，系统研究低Cu、Ni含量的新型高性能多元钛基非晶钎料的成分设计、形成、钎焊性能和连接机理，揭示钛基非晶钎料在钛合金表面的润湿行为、钎焊过程中合金元素的扩散行为、界面反应等与钎料成分、非晶结构的关联，阐明非晶钎料对接头组织结构及力学性能的影响及机制。本项目研究将丰富非晶合金钎料的基础理论、拓展非晶合金的应用、提高钛合金钎焊构件的安全可靠性并扩大其应用范围，具有重要的科学和工程意义。

钛合金广泛应用于航空航天领域，其钎焊连接多采用钛基钎料，但现有商用牌号的钛基钎料中Cu和Ni含量高，导致钎焊接头存在很大脆性。与晶态钎料相比，非晶合金钎料具有成带性好、成分和结构均匀等优点。因此，设计和研究钛合金高强韧钎焊连接用新型钛基非晶钎料是提高钛合金钎焊构件的安全可靠性所面临的关键问题。同时，研究采用非晶钎料钎焊钛合金的连接机理也具有科学意义。本项目针对钛合金高强韧钎焊连接的需求，开展了新型高性能钛基等非晶钎料的成分设计研究，制备出了满足钛合金钎焊温度要求、具有较低Cu和Ni含量、成带性好的Ti–Zr–Cu–Ni–Co–Fe–Al–Sn系、Ti–Zr–Co–Cu–Fe(Sn, Al, V)系和Zr–Ti–Ni–Al(V)系等非晶及非晶/纳米晶钎料，揭示了这些非晶合金钎料的形成机理、晶化及熔化行为与成分的关联。在此基础上，研究了这些非晶钎料成分及钎焊工艺对Ti–6Al–4V钛合金接头的组织结构、力学性能的影响，获得了具有高强度和冲击韧性的接头，揭示了钎焊过程中接头的组织结构演变及钎焊界面反应和连接机理，阐明了接头力学性能与钎料成分、钎焊工艺、接头组织结构之间的关联。发现采用这些新型非晶钎料和适当的钎焊工艺获得的钛合金接头主要由α-Ti和β-Ti构成，没有或者只存在极少量的脆性金属间化合物，元素分布均匀；同时，通过调整钎料成分，可以在钛合金接头中形成均匀的粗大片层组织，对裂纹的扩展起到阻碍作用，从而表现出显著高于采用传统商用牌号钎料获得的钛合金接头的强韧性，表明这些新型非晶钎料具有良好的应用前景。研究结果还进一步说明，可以通过设计新型非晶钎料的成分有效调控接头的组织结构，从而显著改善接头的性能。研究成果对于丰富非晶合金钎料的基础理论、拓展非晶合金的应用、提高钛合金钎焊构件的安全可靠性并扩大其应用范围具有科学和工程意义。