Microstructure and mechanical properties of C_f/SiC composite joints joined using AlCoCrFeNi_2.1 eutectic high-entropy alloy filler via spark plasma sintering

C_f/SiC composites were joined by spark plasma sintering technology using AlCoCrFeNi_2.1 eutectic high-entropy alloy as the joining filler. The typical structure of the joint could be described as C_f/SiC/CrSi₂ + HEAF + Al₄C₃ + C-rich phase/HEAF/CrSi₂ + HEAF + Al₄C₃ + C-rich phase/C_f/SiC. Under the pressure of 30 MPa and at 1450 ℃ for 10 min, the shear strength of the joint was 9.85 MPa at room temperature. However, when a 50 µm thick Ti foil was added to obtain Ti foil/AlCoCrFeNi_2.1/Ti foil composite filler, the joint strength was remarkably increased to 21.15 MPa at room temperature. The formation of TiC phase relieved the thermal stress at the joining interface. Due to the high entropy effect of AlCoCrFeNi_2.1 filler, the central zone of the joint still contained the FCC structure of high-entropy alloy. The existence of the pulsed electric field was beneficial to element diffusion and microstructure homogenization, which improved the mechanical properties of the joint while shortening the joining cycle.