Interfacial reaction behavior and mechanical characterization of ZrO2/TC4 joint brazed by Ag-Cu filler metal

Reliable brazing of ZrO2 ceramic to TC4 alloy is crucial for the wide applications in aerospace industries and biomedical devices. However, the brazing mechanism of ZrO2 ceramic has not been investigated systemically compared to Al2O3 and Si3N4 ceramics. The nature of the reaction products adjacent to ZrO2 ceramic still remains somewhat elusive. In this study, ZrO2 ceramic and TC4 alloy was successfully brazed with inactive AgCu filler metal. The interfacial microstructure of the joints was characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effect of brazing temperature on the microstructure and mechanical properties of the joints were investigated in details. The results revealed that Cu3Ti3O+TiO layers were formed adjacent to ZrO2 ceramic while Ti-Cu IMCs layers were formed at TC4 substrate. With increasing brazing temperature, the thickness of Cu3Ti3O+TiO layers and Ti-Cu IMCs layers increased obviously. The hardness and elastic modulus of reaction phases were characterized by nano-indentation to reveal the plastic deformability. The highest shear strength of 52.2 MPa was achieved when brazed at 870 °C for 10 min.