Interfacial microstructure and joining properties of TiAl/Si3N4 brazed joints

Brazing titanium aluminide to silicon nitride was realized by using inactive AgCu filler metal. The effect of the brazing temperature on the interfacial microstructure and joining strength was investigated. The typical interfacial microstructure of the joint was TiAl/B2 phase/AlCuTi/AlCu2Ti/Ag(s,s) + AlCu2Ti/TiN + Ti5Si3/Si3N4. With an increase of the brazing temperature, the distribution of granular AlCu2Ti intermetallics at the center obviously changed and the thickness of TiN + Ti5Si3 layer adjacent to silicon nitride substrate increased simultaneously. The highest shear strength of 124.6 MPa was achieved with 1133 K brazing temperature and 5 min holding time. In addition, the nucleation of tiny Al3V intermetallics for the precipitation of AlCu2Ti phase was found, which was confirmed beneficial for improving the joining properties.