Interfacial reactions in actively brazed Cu-Al2O3 composites and copper using a newly developed Cu-Sn-Ag-Ti filler alloy

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 TiOx layer with no sensible effect on Ti3(Cu,Al,Sn)3O width.