Microstructure and mechanical properties of Al2O3 ceramic and copper joints brazed with AgCuInTi brazing alloy

Reliable metallurgical bonding between Al2O3 ceramic and copper was achieved by vacuum brazing using Ag-23Cu-14.5In-3.3Ti (wt.%) alloy. The representative interfacial structure of the joint was Al2O3/Ti-3(Cu,Al)(3)O + gamma-TiO/Ag-based solid solution + (Cu,Ag)(7)In-3 + Ag-Cu eutectic + Cu-based solid solution/copper. The interface microstructure evolved with process parameters, including the formation of gamma-TiO and Ti-3(Cu,Al)(3)O, as evidenced by microstructural analysis and etched surface morphology. The relationship between fracture path and shear strength was established by observing the fracture morphology and performing shear strength tests on joints with various process parameters, utilizing the degree of the Ag-based solid solution loss and the thickness of the reaction layer as evaluative factors. When brazed at 760 or 780 degrees C for 20 min using a 100 mu m brazing alloy foil, the brazed joints demonstrated a peak shear strength of 215 +/- 25 MPa, and the fracture predominantly occurred in the Al2O3 matrix and Ti-3(Cu,Al)(3)O layer.