Reactive air brazing of alumina ceramics using Ag–CuO–CeO₂ fillers: Interfacial microstructures and mechanical properties

The development of filler materials and the control of interfacial microstructures have always been research hotspots in the field of ceramic joining via reactive air brazing (RAB). In this study, CeO₂-modified Ag–CuO filler is proposed for RAB of alumina (Al₂O₃) ceramics. The CeO₂ is distributed within the brazing seam. As the CeO₂ content increases, a portion of CeO₂ aggregates at the substrate surface, forming Ag/CeO₂/CuAlO₂/Al₂O₃ interfacial structure. When the CeO₂ content reaches 16 mol.%, the maximum shear strength of the joint reaches 84.1 MPa, representing an approximately 140% increase compared to the joint brazed with CeO₂-free filler. The strengthening mechanism of CeO₂ on the joint includes the regulation of interfacial reactions and the relief of residual stress. Furthermore, after the addition of CeO₂, the content of the brittle CuO phase on the fracture surface is significantly reduced, which contributes to the improvement of joint strength.