Reactions mechanism and mechanical properties of a SiC_f/SiC joint affected by Cu/Ni/Ti elements and inhomogeneous composites

PIP-prepared SiC_f/SiC composite joints were brazed by using Cu-Ni-Ti filler alloys, composed of region I: Ni₁₆Si₇Ti₆ +NiSi₂/NiSi/Ni₃Ti+TiC_x +Cu and region II: TiC_x +Cu and infiltration region. The individual and coupled reactions between Cu/Ni/Ti elements and SiC_f/SiC composites were clarified experimentally and thermodynamically. The infiltration region was first confirmed to be amorphous Cu-Si-C or Si-C matrix, Cu or Cu(C), (Cu, Ni)₁₅Si₄, and Ni₂Si. The joint strength was related to the carbonization and amorphization in the infiltration region and the compound content in region I. Three interfaces of vertical fiber-seam, parallel fiber-seam, and matrix-seam were different because of the inhomogeneous features of SiC_f/SiC composites. The crystallinity of SiC and the residual free carbon affected the reaction kinetics of the Ti element. The PyC coating produced compact TiC_x grains that consequently served as a diffusion barrier for the parallel fibers. The topology of the fibers affected the infiltration region by forming a "capillary action".