Effect of short carbon fiber content on the mechanical properties of TiB 2 ‐based composites prepared by spark plasma sintering

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In this study, TiB 2 ‐30 vol% SiC composites containing 0, 5, 10, and 15 vol% short carbon fibers (C f ) were produced by spark plasma sintering (SPS). The effect of carbon fiber content on microstructure, density, and mechanical properties (micro‐hardness and flexural strength) of the fabricated composites was studied. Scanning electron microscopy (SEM) results indicated that the fibers were uniformly dispersed in the TiB 2 –SiC matrix using wet ball milling before SPS process. Fully dense TiB 2 –SiC–C f composites were achieved by SPS process at 1900°C for 10 min under 30 MPa. With the addition of fibers, the relative density of the composites did not change considerably. Mechanical tests revealed that microhardness was reduced about 19% by the incorporation of carbon fibers, whereas the flexural strength improved significantly. However, the flexural strength diminished by adding carbon fibers above to critical value (5 vol%) due to residual thermal stresses, nonhomogeneous structure and graphitization of carbon fibers. It was found that the composite with 5 vol% C f had the highest flexural strength (482 MPa), which was enhanced by 20% compared with the TiB 2 –SiC composite.