INTERFACIAL REACTIONS IN A TI-6AL-4V BASED COMPOSITE - ROLE OF THE TIB2 COATING

The characterization of TiB2/C-coated SiC fibres and their interface region in a Ti-6Al-4V based composite has been performed by using scanning electron microscopy (SEM), energy-dispersion X-rays (EDX) and Auger electron spectroscopy (AES). The features of the as-received fibre and the reactivity between fibre and matrix occurring during preparation of the composite have been studied in this paper. The interaction of the TiB2 external coating of the fibre with both the adjacent carbon layer and the titanium-based matrix is already appreciable in the as-received composite: TiB needles grow from TiB2 towards the matrix and a new layer containing C, Ti and B appears between TiB2 and C. The thicknesses of the original carbon and TiB2 fibre coatings decrease in the composite from 1 000 nm to 400 and 800 nm, respectively. The TiB2 inhibits the reaction between SiC and Ti: there is no evidence of Si(x)Ti(y) brittle phases.