Mechanical properties and toughening mechanism of WC-doped ZrB2–ZrSi2 ceramic composites by hot pressing

•Nearly full dense WC-doped ZrB2–ZrSi2 composites were fabricated at 1550 °C.•The doping of WC refined the grain size and led to an anisotropic grain growth.•Pull out of the elongated grains improved the fracture toughness.

WC-doped ZrB2–ZrSi2 ceramic composites were fabricated by hot pressing at temperatures ranging from 1450 °C to 1550 °C. The influence of ZrSi2 content on the mechanical properties of the composites was investigated by means of three point bending test and single edge notched-beam test, respectively. The microstructure and phase composition were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. The results revealed that: (i) the highest relative density was 99.5% for the composite fabricated at 1550 °C; (ii) the doping of WC refined the grain size and led to an anisotropic grain growth which was evidenced by the occurrence of elongated grains; (iii) the highest strength and fracture toughness were 585 MPa and 6.87 MPa m1/2, respectively; (iv) the main toughening mechanism was considered as the pull out of elongated grains and the deflection of cracks.