Microstructure and kinetics of induction brazing TiAl-based intermetallics to steel 35CrMo using AgCuTi filler metal

TiAl-based intermetallics joined by vacuum induction brazing using Ag-Cu35.2-Ti1.8 filler alloy at 850-970 °C for 1-10 min was investigated. The interfacial microstructure and reaction kinetics across the brazed joint were comprehensively evaluated. The interfacial microstructure of brazed joints is TiAl/AlCuTi(TiCu)/AlCu₂ Ti(TiCu)/Ag solid solution/AlCu₂Ti(TiCu)/TiC/35CrMo. According to the experimental observations, silver would not react with the TiAl substrate, but copper reacted strongly with the TiAl substrate, forming continuous reaction layer. The degree of interfacial reaction of TiAl/Ag-Cu35.2-Ti1.8 is related to the configuration of AlCu₂ Ti reaction layer and the amount of TiAl/Ti₃Al phase interface in the TiAl substrate under the same technological conditions. The configuration and the size of AlCuTi phase have relation to the configuration and the amount of TiAl/Ti₃Al lamellar colony. The visible acicular AlCuTi phase can be generated by the approximate lamellar structure with low Al content, which is beneficial to the joining of the TiAl substrate.