Characteristics of spark plasma sintered ZrB2-SiC-SCFs composites

Abstract The effects of short carbon fibers on sinterability, flexural strength, fracture toughness and thermal shock resistance of spark plasma sintered ZrB2-SiC composites were investigated. Four samples containing 10, 20, 30 and 40 vol% of short carbon fibers (SCFs) were consolidated by spark plasma sintering at 1800 °C for 6 min under an external pressure of 40 MPa. Mechanical properties of the samples including flexural strength and fracture toughness were measured via three-point bending strength test and indentation method, respectively. Fractographical investigations were carried out via scanning electron microscopy. Thermal shock resistance of the samples was also studied via quenching method. Obtained results showed that a higher fraction of SCFs (10 vol% SCFs to 40 vol% SCFs) leads to lower relative density (90.8–89.1%) and higher amount of open porosity (7.8 vol% to 8.9%). It is also indicated that SCFs ascent from 10 to 40 vol% improve the fracture toughness from 4.1 to 5.1 MPa m1/2 by promoting toughening mechanisms such as crack deflection, branching, and pull-out. Finally, it was cleared that by SCFs ascent from 10 to 40 vol%, ΔTC increases from 530 °C up to 600 °C.