Abstract: A novel method for fabricating “core-rim” structured toughened (Ti, Ta)C-(Ti, Ta)B₂-SiC based ceramics was developed, employing in-situ reaction hot-pressing of TiC, TaB₂, and Si powders at 1600 °C. This study explored the impact of varying TaB₂ and Si concentrations on the microstructure and mechanical properties of the ceramics and clarified the formation mechanism of the “core-rim” structure. In this process, the reaction process of TiC and TaB₂ powders and the reaction and solid solution formation of (Ti, Ta)C and (Ti, Ta)B₂ occur simultaneously. TiC/TaC react with Si to form (Ta, Ti)Si₂ and β-SiC phases through further solid solution reactions. The presence of β-SiC and (Ta, Ti)Si₂, coupled with low-temperature in-situ reactions, restricts grain growth and refines the microstructure. Adding 10 mol% TaB₂ results in incomplete diffusion of TaC in TiC, leading to the distinct “core-rim” structure, with cracks propagating preferentially along the rim. The β-SiC and plate-like (Ti, Ta)B₂ structures formed in-situ reactions significantly enhance the fracture toughness of the ceramics. The TiC-32 mol% Si-10 mol% TaB₂ (10TB-16) exhibited superior fracture toughness of 6.97±0.52 MPa m^1/2, the TiC-16 mol% Si-30 mol% TaB₂ (30TB-16) exhibited superior flexural strength of 835±39 MPa, excellent fracture toughness of 6.68±0.66 MPa m^1/2, offering new insights into optimizing the strength and toughness of ceramics.

Key words: “Core-rim”, structured toughened;, In-situ reaction, Plate-like (Ti, Ta)B₂, Superior mechanical properties