On the role of carbon diffusion during fiber/matrix reaction in SiC fiber reinforced Ti-based MMCs

摘要

There are numerous reports dealing with the reaction of Ti alloy matrices with the carbon-rich protective coating of the reinforcing SiC fibers. The focus of most of these past studies was on the reaction zone products. However, simple calculations based on available diffusivity data indicate that the diffusion of carbon from SiC fiber coating into Ti alloy matrix is not limited to the near-fiber region, but can occur over a long range relative to the fiber diameter. In this paper, experimental work involving appropriate heat treatments of a variety of Ti-based composites is reported and microstructural evidence for long range diffusion of carbon is presented in the form of carbide precipitaion in the Ti-matrix. It is also shown that the increased carbon content of the titanium alloy matrix leads to significant microstructural changes and markedly different heat treatment response of SiC/Ti composites as compared to fiberless Ti alloy matrix.