Interfacial strengthening mechanism of C/C/Nb0.74CoCrFeNi2/Nb brazed joints: Stress-relieving effects of the FCC phase

Joining ceramics and metals has long been a key issue for manufacturing structures that are resistant to high temperature. This study joined a carbon-fiber-reinforced carbon-matrix (C/C) composite and Nb using a Nb0.74CoCrFeNi2 eutectic high-entropy alloy filler, and the evolution mechanism of the microstructure and mechanical properties of the joints were systematically studied. The eutectic structure composed of face-centered cubic (FCC) and Laves phases gradually disappeared with the increasing temperature, while the Nb(s,s) layer thickness increased gradually. The lattice mismatch was similar to 97% and similar to 2.8% at the Cr23C6/C/C and FCC/C/C interfaces, respectively. Considering differences in the coefficient of thermal expansion and lattice mismatch, an increase in FCC phase content at the C/C interface is conducive to reinforcing the joint strength. At 1260 degrees C, the combined effects of the highly deformable FCC phase and high-strength Cr23C6 increased the strength of the mixing zone, causing fracture to occur in the Nb(s,s) layer. These results are expected to contribute to further improving the joining of dissimilar materials.

Automated summary

This study successfully joined a carbon-fiber-reinforced carbon-matrix (C/C) composite and Nb using a Nb0.74CoCrFeNi2 eutectic high-entropy alloy filler. The research found that adjusting the content of the face-centered cubic (FCC) phase can enhance the strength of the joint. The results of the study are of great significance for improving the joining of dissimilar materials.