Characterization of reactive spark plasma sintered (Zr,Ti)B₂–ZrC–SiC composites

This investigation aims to evaluate the influence of SiC introduction on the microstructure development, mechanical characteristics, and densification behavior of (Zr,Ti)B₂–ZrC materials. Two specimens, with/without SiC addition, were manufactured from the starting materials of ZrB₂ and TiC by reactive spark plasma sintering (SPS) at 1800 °C under 30 MPa for 5 min. Both samples reached relative density values higher than 99%; however, the SiC addition improved this value by ~0.5%, standing at 99.9%. The SiC incorporation into the (Zr,Ti)B₂–ZrC system led to an ultrahigh temperature ceramic (UHTC) with considerable hardness and elastic modulus. The TiC additive was completely consumed over the sintering process, participating in the in-situ formation of TiB₂ and ZrC as a result of a chemical reaction with the ZrB₂ matrix. Thanks to the diffusion of Ti and Zr atoms into the ZrB₂ and TiB₂ phases, respectively, a solid-solution of (Zr,Ti)B₂ formed with various compositions in different areas. Thanks to the synergistic effects of grain refinement and solid-solution formation, the (Zr,Ti)B₂–ZrC–SiC sample reached excellent mechanical properties such as an elastic modulus of 495 GPa and a hardness of 31.2 GPa.