Interface reaction studies of B₄C/B and SiC/B fiber-reinforced Ti₃Al matrix composites

The interfacial chemical reactions of the silicon-carbide-coated boron (SiC/B) and boron-carbide-coated boron (B₄C/B) fibers with the Ti₃Al + Nb matrix were investigated. The microstructure as well as the chemical composition throughout the reaction zone were identified. The reaction kinetics were quantified, and the effect of reaction zone thickness on the fracture behavior of the composites was assessed. It was found that an extensive reaction resulting in complex multilayer reaction products occurred owing to the rapid diffusion of constituent atoms in the fibers and the matrix. The reaction is diffusion controlled with activation energies of 47 and 40 kcal mol^-1 for the (SiC/B)-(Ti₃Al + Nb) and (B₄C/B)-(Ti₃Al + Nb) composites respectively. The results reported can be used as guidelines for the selection of processing parameters to avoid the excessive fiber-matrix reaction, determination of service life expectancy and development of ways to control these reactions. © 1989.