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, CeO 2 -modified Ag–CuO filler is proposed for RAB of alumina (Al 2 O 3 ) ceramics. The CeO 2 is distributed within the brazing seam. As the CeO 2 content increases, a portion of CeO 2 aggregates at the substrate surface, forming Ag/CeO 2 /CuAlO 2 /Al 2 O 3 interfacial structure. When the CeO 2 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 CeO 2 -free filler. The strengthening mechanism of CeO 2 on the joint includes the regulation of interfacial reactions and the relief of residual stress. Furthermore, after the addition of CeO 2 , the content of the brittle CuO phase on the fracture surface is significantly reduced, which contributes to the improvement of joint strength.