Abstract: The composite fillers with different proportions of Cu and B powders were used to braze Al₂O₃ to TC4 alloy at 930℃ for 10 min.The joining and microstructure of Al₂O₃/TC4 alloy joints were observed and analyzed by SEM and EDS.The results show that Al₂O₃/TC4 alloy joint interfacial microstructure is Al₂O₃/Ti₃(Cu, Al)₃O/Ti₂Cu+Ti₂(Cu, Al)/Ti+Ti₂(Cu, Al)+Ti(Cu, Al)+AlCu₂Ti+Ti₂Cu/Ti₂Cu+AlCu₂Ti+TiB/Ti+Ti₂Cu/TC4 alloy.Mutual diffusion of Cu atoms from composite filler and Ti atoms from TC4 alloly occurs during brazing process.Cu-Ti compounds with different components were formed in Al₂O₃/TC4 alloy joints.B reacts with Ti atoms in liquid, and in situ synthesizes TiB whiskers in joint, which mainly distribute into Ti₂Cu and AlCu₂Ti.With the increasing of TiB content, Ti₂(Cu, Al) content increases, and becomes continuous gradually.At the same time, that moves to Al₂O₃ side.