Microstructure of Al₂O₃-TiC composite ceramics and Q235 steel diffusion bonded interface

The diffusion bonding of Al₂O₃-TiC composite ceramics to Q235 low carbon steel by using Ti/Cu/Ti as multi-interlayer was carried out by liquid phase diffusion bonding technology.The microstructure,fracture morphology and phase constituents for Al₂O₃-TiC/Q235 diffusion bonded joint were studied with scanning electron microscope,electron probe microanalysis and X-ray diffraction.The test results indicate that the Al₂O₃-TiC composite ceramics tightly combines with Q235 low carbon steel,and the interface both on the Al₂O₃-TiC and Q235 side seems to be continuous,straight and free of the micro-voids,cracks and unbonded areas.The various new phases,such as TiO,Ti₃Al,Cu₂Ti₄O and Cu₃Ti₃O,are formed near the interface of the Al₂O₃-TiC/Q235 joint.The formed TiO phase and the complex structure oxides of Cu₂Ti₄O and Cu₃Ti₃O have metallic characteristics,which are very important to promote reliable bonding of Al₂O₃-TiC with Q235.The shear strength of the joints reaches 143 MPa,the fracture reveals brittle features and the fracture of the Al₂O₃-TiC/Q235 joint occurs in Al₂O₃-TiC near the interface.