Microstructure evolution and mechanical properties of ZrO2/TiAl joints vacuum brazed by Ag-Cu filler metal

Reliable brazing of ZrO2 ceramic and TiAl alloy was achieved using inactive AgCu filler metal. The effect of brazing temperature on the interfacial microstructure and mechanical properties of ZrO2/TiAl joints were investigated. The results indicated that the representative microstructure of the joint was TiAl alloy/γ-TiAl/AlCuTi/AlCu2Ti/Ag(s,s)+AlCu2Ti+AlCu4/Cu3Ti3O+TiO/ZrO2 ceramic. With increasing brazing temperature, the thickness of reaction zone adjacent to TiAl substrate and continuous reaction layers next to ZrO2 ceramic increased obviously. In addition, the AlCu2Ti particle phase coarsened and aggregated in brazing seam at higher temperature. The Ti and Al dissolved from TiAl substrate have an enormous effect on microstructure evolution of ZrO2/TiAl joints and the mechanism is discussed. The maximum average shear strength reached 48.4 MPa when brazed at 880 °C for 10 min.