Effect of Cu interlayer with different thickness on microstructure and properties of Al2O3/Kovar joints brazed with Cu–Ti/Cu/BNi-2 composite filler

In this study, a Cu–Ti/Cu/BNi-2 composite filler was employed to braze Al2O3 ceramics and Kovar alloy, aiming to prevent excessive reaction between active Ti and Kovar alloy. The investigation focused on the effects of varying Cu interlayer thickness on microstructure and mechanical properties. The results show that the typical microstructure of the joint is Al2O3/Ti–O/Cu3Ti3O /Ti-rich + Cu(s, s)/Ni3Ti + TiB2/CrB + Ni(s, s)/Kovar alloy. Notably, when the thickness of the Cu layer was 100 μm, the joint strength significantly increased to 128 ± 7 MPa, which represented a remarkable 50.5