Joining of SiO2f/SiO2 composite to Al2O3 ceramic using AgCu-Ti brazing filler metal

SiO2f/SiO2 composite was joined to Al2O3 ceramic using AgCu-Ti active filler at brazing temperature of 1153 K for 10 and 60 min, respectively, and sound joints were achieved. It was found that a thin reaction layer had been formed close to each of the joined materials, and the brazing seam matrix was composed of homogeneous Ag-Cu eutectic alloy. The joint interface was analyzed by SEM, EDS, and XRD. The typical interface structure of joint brazed at 1153 K for 10 min could be described as the following sequence: SiO2f/SiO2 -> TiO2 + Ti5Si4 -> TiO2 + Cu3Ti3O -> Ag-Cu eutectic alloy -> (Ti-O) + (Ti-Cu-O) -> Al2O3. However, Cu2Ti4O but not Cu3Ti3O was detected in the joints brazed at 1153 K for 60 min. Besides, the reaction layers of joint brazed at 1153 K for 60 min were much thicker than those for 10 min. The SiO2f/SiO2-Al2O3 joints brazed at 1153 K for 10 min showed an average shear strength of 38.6 MPa, evidently higher than that (26.0MPa) brazed at 1153 K for 60 min.