Joining of C_f/SiC composites using AlCoCrFeNi_2.1 eutectic high-entropy alloy filler by spark plasma sintering

AlCoCrFeNi_2.1 eutectic high-entropy alloy was introduced to join C_f/SiC composite by spark plasma sintering technique. The influence of holding times on microstructure, shear strength and fracture behavior of the joints was studied. When held for 7 min, the typical microstructure of the C_f/SiC-AlCoCrFeNi_2.1-C_f/SiC joint was C_f/SiC composite → CrSi₂ + FCC + Al₈Cr₅ + graphite → CrSi₂ + FCC + Al₈Cr₅ → CrSi₂ + FCC + Al₈Cr₅ + graphite → C_f/SiC composite. As the holding time extended, the Ni–Si and Fe–Si brittle phases in the joint gradually reduced, and the diffusion transition layer continued to thicken. The maximum joint strength was 23.9 MPa, which was obtained at 1450°C for 7 min. Analyzed by scanning electron microscopy and energy dispersive spectroscopy, the fracture modes of the joints joined at different holding times were all brittle fracture.