Interfacial reactions in actively brazed Cu-Al 2 O 3 composites and copper using a newly developed Cu-Sn-Ag-Ti filler alloy

Abstract

In dissimilar brazing, the differences in physical properties between the components lead to residual stresses. An active filler alloy Cu-20.5Sn-20Ag-3.5Ti was developed to braze the Cu-Al₂O₃ composites (containing 25 and 50 volume pct. Al₂O₃) to copper. Two mechanisms were proposed for chemical bonding as a result of alumina reinforcements reduction by the active titanium, including the formation of Ti₃(Cu,Al,Sn)₃O layer beside the Ti₂O in Cu/Cu-25%Al₂O₃ joints; and the solidification of Ti₃(Cu,Al,Sn)₃O in the vicinity of TiO layer/Cu₄Ti islands in the Cu/Cu-50%Al₂O₃ joints. Some intermetallic compounds such as Cu₃Ti₂ and Cu₄₁Sn₁₁ are formed/coarsened with an extra increase in brazing temperature. An increase in brazing time improves the thickness of the TiO_x layer with no sensible effect on Ti₃(Cu,Al,Sn)₃O width.