Microstructure and mechanical properties of Al2O3/Cu joints brazed with Ag–Cu–Ti+Zn composite fillers

In this study, Al2O3 ceramic and Cu bars were brazed with newly designed Ag–Cu–Ti(ABA)+Zn composite fillers. Systematic analysis of the microstructure of the brazed joints indicated that the volatilization of Zn atoms during the brazing process could promote the spreading of liquid brazing fillers on the surface of the Al2O3 ceramic, resulting in a uniform dendritic interfacial structure. The typical interfacial structure was an Al2O3/TiO/(Cu, Al)3Ti3O+Ag(s, s)/Cu interface. Notably, the tensile strength was improved to 20.89 MPa for Al2O3/Cu joint brazed with ABA+Zn composite fillers at 900 °C for 20 min, approximately 67.6% higher than the sample brazed without Zn foil. In this case, the fracture model was straight and sharp-angled inside the Al2O3 ceramic. In addition, the joint strength decreased with increased brazing temperatures from 900 to 940 °C.