Enhancing SiC/Nb brazed joints by negative thermal expansion (Sr_0.2Ba_0.8)TiO₃ nanoparticle-coated Cu foam

Negative coefficient of thermal expansion (Sr_0.2Ba_0.8)TiO₃ (SBT) nanoparticles are produced by ball milling and twice sintering process and coated with Cu foam (Cu_f) as an interlayer for brazing SiC and Nb. The influence of SBT content on the microstructural, shear strength, and fracture mechanism of SiC/Nb joints is investigated. In particular, SBT/Cu_f foam is utilized to modify the coefficient of thermal expansion of the AgCuTi/SBT/Cu_f/AgCuTi composite filler, resulting in a reduction of residual stresses in the joints. The residual stresses at the joints are calculated as well as analyzed the mechanism of residual stress relief by SBT. Following the introduction of the interlayer, the maximum shear strength of the joint is approximately 72 MPa, which is 164 % higher than the performance of the joint with uncoated SBT.