Effect of TiO2 addition on microstructure and mechanical properties of Al2O3 ceramic joints brazed with Ag‐CuO fillers

Abstract

AbstractIn our work, 0.5 mol.% TiO2 was added to Ag‐xCuO (x = 2, 4, 8 mol.%) fillers whose compositions at 1050°C were in the L2 single liquid phase region, the boundary of the miscible phase region, and the L1+L2 miscible phase region, respectively. The role of TiO2 was derived by comparing the quenching microstructure of the fillers on the Al2O3 ceramics and the effect on the interfacial microstructure and shear strength of the joints before and after the addition of TiO2. The results showed that the TiO2 would dissolve into the CuO‐rich L1 liquid phase of the filler, leading it to spread outside the molten droplet. When brazing with Ag‐4CuO‐0.5TiO2 filler, the CuO at the joint interface almost completely disappeared, and the shear strength of the joint was significantly reduced. In contrast, the joint strength showed a small increase when using Ag‐8CuO‐0.5TiO2 filler, as the excess CuO at the interface of the brazed joint was reduced. When the filler composition was in the L2 single liquid phase region, CuO was diffusely distributed throughout the molten droplet. TiO2 was hardly contacted with CuO and its addition had no significant effect on the interfacial microstructure and the shear strength of the joints.