| In order to meet the requirement of joining SiO2 ceramic to 30Cr3 high-tensile steel and TC4 titanium alloy used in automobile engine and aero-engine, active brazing of SiO2 ceramic to 30Cr3 high-tensile steel and TC4 alloy was carried out using AgCuTi and TiZrNiCu brazing filler metal. The mechanism and technology of active brazing and formation of the interface were studied. The microstructure and properties of the joints were discussed by means of experimental examination and theoretical analysis.The microstructure of the joints was analyzed by means of SEM, EPMA and XRD. The results showed: the microstructure of SiO2 cemamic/ AgCuTi/ 30Cr3 high-tensile steel was SiO2 ceramic/ TiSi2+Ti4O7/ Ti2Cu+Cu3Ti3O/ Ag(s. s)+Cu(s. s)/ TiFe2/ 30Cr3 high-tensile steel; the microstructure of SiO2 ceramic/ TiZrNiCu/ TC4 alloy was SiO2 ceramic/ Ti2O+Zr3Si2+Ti5Si3/ (Ti, Zr)+TiZrNiCu/ Ti(s. s)/ TiZrNiCu+Ti(s. s)+Ti2(Cu, Ni)/ TC4 alloy; and the microstructure of SiO<sub>2 ceramic/ AgCuTi/ TC4 alloy was SiO2 ceramic/ TiSi2+Ti4O7/ TiCu+ Cu2Ti4O/ Ag(s. s)+Cu(s. s)/ TiCu/ Ti2Cu/ Ti+Ti2Cu/ TC4 alloy .Based on the interface structures identified in the joins, formation mechanism and technology for interface structure were discussed. And the changes of microstrure were analyzed at different brazing parameters.The shear strength was tested to evaluate the mechanical poperty of the joints. The results showed that when the brazing parameters changed, The shear strengths of the joints increased and then decreased with the brazing time increased or holding time prolonged. When the brazing temperature was 900℃and holding time was 5 min, the maximum shear strengths of the SiO2 cemamic/ AgCuTi/ 30Cr3 high-tensile steel joint and SiO2 ceramic/ AgCuTi/ TC4 alloy joint could be achieved, which are 37MPa and 27MPa. When the brazing temperature was 880℃and holding time was 5 min, the maximum shear strengths of SiO2 ceramic/ TiZrNiCu/ TC4 alloy joint was achieved at 23 MPa.The fracture path of the brazed joints was discussed by using SEM, EPMA analysis, the results showed that brittle fracture took place in two main areas, which were SiO2 ceramic base material and the layers which appeared adjacent to the SiO2 ceramic.
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