Characterization of ZrB₂–TiC composites reinforced with short carbon fibers

Solid solution formation, phase evolution, microstructure development, and mechanical behavior of ZrB₂–TiC composites with/without carbon fiber additive were investigated. Fully dense composites were manufactured by spark plasma sintering route under 40 MPa load at 1900 °C for 420 s. FESEM and XRD studies were carried out to unveil the densification and toughening mechanisms in the sintered specimens. Results showed that the addition of only 1 wt% short carbon fibers increased the hardness from 21.8 GPa to 23.5 GPa. Moreover, a 3 % enhancement in the indentation fracture toughness was also observed due to the incorporation of short carbon fibers. The in-situ formation of ZrC and TiB₂ phases were identified and related to a chemical reaction between the ZrB₂ and TiC constituents. The solid solution development between the ZrB₂ matrix and the in-situ formed TiB₂ was also proved by the microstructural observation and the shifted peaks of ZrB₂ in the XRD patterns.