The microstructural and mechanical behavior of in-situ synthesized ZrB2-ZrC and ZrB2-SiC-ZrC composites: A comparative study

In the present investigation, the ZrB2-ZrC and ZrB2-SiC-ZrC based composites were fabricated via an in-situ reduction mechanism using ZrO2, B4C, Si, and graphite fine powder at 1900 degrees C in an argon atmosphere. The boro/carbothermal reduction produced nano-sized ZrC grains with ZrB2 particles, whereas the incorporation of Si content produced nano-sized homogeneous distributed SiC grains with ZrB2-ZrC particles. In the ZrB2-based composite densification, microstructure, mechanical, and chemical state identification of elements were inves-tigated. The densification of the samples was enhanced with the formation of ZrC and SiC content, which was correlated with the micrographs and mechanical properties of the samples. The chemical state identification confirms the trace amount of intermediate zirconium oxycarbide in the ZrB2-based composite. Compared to binary ZrB2-ZrC composite, ZrB2-SiC-ZrC composite has finer microstructure and higher densification. The strength of the ZrB2-ZrC and ZrB2-SiC-ZrC composite was decreased by 458 MPa and 406 MPa, respectively. Similarly, the indentation hardness of the samples was increased by 14.2 GPa-15.3 GPa, and fracture toughness was 5.5 +/- 0.5 MPa m1/2 to 6.15 +/- 0.4 MPa m1/2.