MICROSTRUCTURAL OBSERVATIONS OF REACTION ZONES IN TI-BASED METAL-MATRIX COMPOSITES

The interaction between Ti-alloy matrices and ceramic particulate and fibres in Ti-based metal-matrix composites (MMCs) is reviewed. It is concluded that the stability of surface-treated SiC fibres is adequate for some applications of MMCs, but no other fibres have yet been developed which are useful additions to Ti alloys. Although there is less interest at this stage in particulate-reinforced Ti MMCs, there are two ways in which useful particulate MMCs could be developed. First, the approach used in fibre-reinforced composites, of using special coating techniques to stabilize the particulate against any reaction with the matrix. Second, either C or B additions could be used, both of which give rise to particulate phases which are stable in the presence of a Ti matrix, and which can therefore be manufactured using a wider range of process routes than is possible for other composites. The significance of these conclusions with regard to the ability to shape particulate composites into final products is briefly discussed.