Effect of ZrC Content on the Microstructure and Mechanical Properties of (Ti_0.2Zr_0.2Nb_0.2Hf_0.2Ta_0.2)B₂-SiC

This study investigates the effect of ZrC content on the microstructure and mechanical properties of (Ti_0.2Zr_0.2Nb_0.2Hf_0.2Ta_0.2)B₂-SiC ceramics. Interrupted sintering experiments and diffusion couple tests are employed to elucidate the densification behavior. Results indicate that significant cationic interdiffusion occurs between the (Ti_0.2Zr_0.2Nb_0.2Hf_0.2Ta_0.2)B₂ and ZrC during sintering. Specifically, Zr atoms from ZrC migrate into the (Ti_0.2Zr_0.2Nb_0.2Hf_0.2Ta_0.2)B₂ lattice, while Ti, Nb, Hf, and Ta atoms from boride concurrently diffuse in the opposite direction into the ZrC phase. As a consequence of this interdiffusion, a dual-phase multi-principal-element ceramic consisting of non-equimolar (Ti,Zr,Nb,Hf,Ta)B₂ and (Ti,Zr,Nb,Hf,Ta)C is formed in situ. The relative density of the samples increases from 95.3% to 99.5% with the ZrC content increasing from 10 vol% to 30 vol%, indicating that an appropriate amount of ZrC addition effectively promotes densification. For the sample with 30 vol% ZrC addition, the grain sizes of (Ti,Zr,Nb,Hf,Ta)B₂ and (Ti,Zr,Nb,Hf,Ta)C are 0.88 ± 0.31 μm and 0.66 ± 0.24 μm, respectively. And the flexural strength reaches 767 ± 37 MPa, representing an 86% improvement compared to the sample with 10 vol% ZrC addition. The enhanced properties can be attributed to the elemental interdiffusion between (Ti_0.2Zr_0.2Nb_0.2Hf_0.2Ta_0.2)B₂ and ZrC, which promotes mass transfer during sintering, thereby accelerating densification and optimizing the microstructure.