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

PIP-prepared SiCf/SiC composite joints were brazed by using Cu-Ni-Ti filler alloys, composed of region I: Ni16Si7Ti6 +NiSi2/NiSi/Ni3Ti+TiCx +Cu and region II: TiCx +Cu and infiltration region. The individual and coupled reactions between Cu/Ni/Ti elements and SiCf/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 fiberseam, and matrix-seam were different because of the inhomogeneous features of SiCf/SiC composites. The crystallinity of SiC and the residual free carbon affected the reaction kinetics of the Ti element. The PyC coating produced compact TiCx 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".