Improving the mechanical properties of reactive sintered (Hf, Ta)B2-(Hf, Ta)C-SiC multi-phase ceramics by synergistic reinforcing effect of multi-component borides and carbides

Low-temperature sintering and phase/microstructure tailoring of multi-element ultra-high temperature ceramics remain challenging, restricting the improvement of mechanical properties and the development of ultra-high temperature ceramic materials. In this work, a novel low-temperature reactive sintering technology was used to tailor the content of multiple borides and carbides in (Hf, Ta)B 2 -(Hf, Ta)C-SiC ceramics. It was found that the introduction of borides promoted the densification process of multi-phase ceramics. With the increase of borides content, the grain size of multi-phase ceramics gradually increased. The introduction of moderate amount borides helped to form a uniformly refined microstructure. When the molar ratio of borides to carbides was 2:1, the flexural strength and fracture toughness of multi-phase ceramics were the highest, which were 487.57 ± 38.3 MPa and 5.04 ± 0.09 MPa·m 1/2 , respectively. The main strengthening and toughening mechanisms included pullout of (Hf, Ta)B 2 grains and crack deflection.