Abstract
Abstract The combined effects of SiC particles and chopped carbon fibers (C f ) as well as sintering conditions on the microstructure and mechanical properties of spark plasma sintered ZrB 2 -based composites were investigated by Taguchi methodology. Analysis of variance was used to optimize the spark plasma sintering variables (temperature, time and pressure) and the composition (SiC/C f ratio) in order to enhance the hardness of ZrB 2 –SiC–C f composites. The sintering temperature was found as the most effective variable, with a significance of 83%, on the hardness. The hardest ZrB 2 -based ceramic was achievable by adding 20 vol% SiC and 10 vol% C f after spark plasma sintering at 1850 °C for 6 min under 30 MPa. Fracture toughness improvement were related to the simultaneous presence of SiC and C f phases as well as the in-situ formation of nano-sized interfacial ZrC particles. Crack deflection, crack branching and crack bridging were detected as the toughening mechanisms. A Vickers hardness of 14.8 GPa and an indentation fracture toughness of 6.8 MPa m 1/2 were measured for the sample fabricated at optimal processing conditions.
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