Microstructure and mechanical properties of Cf/SiC composite joints joined using AlCoCrFeNi2.1 eutectic high-entropy alloy filler via spark plasma sintering

Abstract

Cf/SiC composites were joined by spark plasma sintering technology using AlCoCrFeNi2.1 eutectic high-entropy alloy as the joining filler. The typical structure of the joint could be described as Cf/SiC/CrSi2 + HEAF + Al4C3 + C-rich phase/HEAF/CrSi2 + HEAF + Al4C3 + C-rich phase/Cf/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/AlCoCrFeNi2.1/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 AlCoCrFeNi2.1 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.