Effect of brazing time on microstructure and bonding strength of brazing interface between Al_2O_3 and carbon steel

Al2O3and carbon steel were brazed using Cu-Ti as active filler. The microstructure of the brazing zone of Al2O3 and carbon steel was characterized by means of transmission electron microscopy and scanning electron microscopy with energy dispersive spectrometer system and X-ray diffraction. The effects of brazing temperature( 1050 ℃) and time( 10-40 min) on the microstructure and the shear strength of the brazing zone were investigated. The results show that the good microstructure and higher shear strength for the brazing zone can be obtained at brazing temperature of 1050 ℃ for brazing time of 30 min. Three layers,which are reaction layer with Ti4Fe2 O close to the ceramic Al2O3,brazing alloy layer of Cu solid solution and Ti4Fe2 O,and diffusion layer with Ti Fe2 close to carbon steel,are formed at the brazing zone. The microstructure of the brazing zone is dense and its shear strength reaches 99 MPa.