C_f/Si-Zr composite brazing filler for SiC_f/SiC composite joints: Microstructure, interface reaction and high-temperature performance

High-temperature joining of SiC_f/SiC composites is essential for their integration in advanced heat-resistant systems; however, reliable joints require both robust filler design and fundamental understanding of interfacial stability under service conditions. Here, we introduce a chopped carbon fiber reinforced Si–Zr composite filler (C_f/Si–Zr) that transforms into the SiC/Si–Zr composite within the joint during brazing process. Concurrently, a coarse-SiC layer and a diffusion zone develop at the SiC_f/SiC-filler interface. The resulting joints exhibit shear strengths of 87 ± 2 MPa at 1000 °C and 60 ± 3 MPa at 1200 °C-substantially outperforming joints brazed with unreinforced Si-Zr alloy. After 20 thermal-shock cycles between room temperature and 1000 °C, no microcracking or debonding is observed, and the residual shear strength remains > 50 MPa. Thermodynamic calculations and finite-element modeling reveal that the in-situ formed SiC homogenizes interfacial bonding and relaxes macroscopic thermal-stress mismatch, thereby enhancing joint durability. These findings establish C_f/Si-based composite fillers as an effective route toward high-temperature, damage-tolerant joining of SiC_f/SiC components.