钛/钢异种金属超声辅助双光束激光熔焊-熔钎焊双界面调控及成形机制研究

There are some problems in existing welding methods of Ti/Fe dissimilar metals, such as the Ti-Fe brittle compound formation, large residual stress, low welding efficiency, and narrow range of welding parameters. To improve the welding quality and efficiency of Ti/Fe dissimilar metals, a new welding method named as ultrasonic vibration assisted dual beam laser welding- penetration brazing is proposed in this work. A hybrid joint comprising two metallurgical bonding zones based on two different kinds of joining mechanisms was obtained by once welding. The Ti and V alloys are joined by fusion zone, while laser penetration brazing is responsible for joining V and Fe alloys. V interlayer with high melting point did not melt completely, acting as a diffusion barrier between the Ti and Fe. The microstructure morphologies and macro/micro segregation of Ti/Fe joints are influenced by ultrasonic vibration, improving the mechanical properties of the joint. The mechanisms of the effect of ultrasonic vibration on thermal and mass transfer behavior, metastable phase precipitation at the V/Fe interface, and macro/micro segregation at the Ti/V interface are systematically studied by the combined method of experimental and theoretical analysis. The physical model of the wetting and reaction at the V/Fe interface via ultrasonic assisted was established, and the correlation among ultrasonic assisted double beam welding parameters, macro/micro structure and mechanical properties of the joint are revealed. Then, the high quality joints of Ti/Fe can be achieved under the wide range of welding parameters. Research results are provided a new method of welding Ti/Fe dissimilar metals and have important theoretical significance and practical value in promoting the application of lightweight structure.

针对现有钛/钢异种金属焊接方法存在易产生脆性金属间化合物、残余应力大、焊接效率低、工艺窗口窄等问题，本项目提出超声辅助双光束激光熔焊-熔钎焊接方法，即通过双光束一次焊接获得Ti/V熔化焊与V/Fe熔钎焊两个连接界面，未熔V可以有效阻碍熔池中Ti和Fe混合抑制Ti-Fe脆性化合物形成，超声振动改善熔钎焊界面组织形态及熔化焊界面宏/微观偏析。通过系统研究超声对熔钎焊界面热质传输行为、熔钎焊界面亚稳相析出行为和熔化焊界面宏/微观偏析的影响机制，建立超声作用下熔钎焊界面润湿反应模型，揭示超声辅助双光束焊接参数、接头宏/微观组织结构、接头力学性能之间内在关联，拓宽工艺窗口，实现钛/钢高质高效连接。研究成果为异种难焊材料连接提供新的思路和方法，对促进轻量化结构应用具有重要理论意义及实用价值。

针对现有钛/钢异种金属焊接方法存在易产生脆性金属间化合物、残余应力大、焊接效率低、工艺窗口窄等问题，本项目提出超声辅助双光束激光熔焊-熔钎焊接方法，即通过双光束一次焊接获得Ti/V熔化焊与V/Fe熔钎焊两个连接界面，未熔V可以有效阻碍熔池中Ti和Fe混合抑制Ti-Fe脆性化合物形成，超声振动改善熔钎焊界面组织形态及熔化焊界面宏/微观偏析。通过系统研究超声对熔钎焊界面热质传输行为、熔钎焊界面亚稳相析出行为和熔化焊界面宏/微观偏析的影响机制，建立超声作用下熔钎焊界面润湿反应模型，揭示超声辅助双光束焊接参数、接头宏/微观组织结构、接头力学性能之间内在关联，拓宽工艺窗口，实现钛/钢高质高效连接。研究成果为异种难焊材料连接提供新的思路和方法，对促进轻量化结构应用具有重要理论意义及实用价值。