Abstract: High-entropy carbides are promising candidates for high-temperature structural applications owing to their exceptionally high melting points and outstanding thermal stability. However, their intrinsic brittleness severely restricts practical use. To address this limitation, carbon fiber reinforcement has emerged as a viable approach to enhance fracture toughness. In this study, pyrolytic carbon (PyC) was employed as a protective layer for the carbon fibers, while a TiC interface layer was incorporated to strengthen interfacial bonding. During high-temperature sintering, elemental diffusion at the interface promotes chemical interactions. The findings reveal that TiC diffusion catalyzes the graphitization of PyC, resulting in the in-situ formation of a multilayer graphene (MLG) bonding structure at the fiber-matrix interface. Molecular dynamics simulations elucidate that MLG formation proceeds via a generation-redecomposition mechanism involving TiC. This in-situ-formed MLG significantly enhances interfacial adhesion, enabling the Cf/(TiZrHfNbTa)C-SiC composite to achieve remarkable mechanical performance, with a flexural strength of 652.87 MPa and a fracture toughness of 7.64 MPa m^1/2. Furthermore, the MLG significantly improved thermal conductivity, endowing the composite with excellent thermal shock resistance (with a critical temperature difference, T_c, of 692 °C) and superior ablation resistance (with linear and mass ablation rates of 3.75 μm s^-1 and 0.16 mg s^-1, respectively). © 2026 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Key words: High-entropy carbide, Carbon fiber, Multi-layer graphene, Interface, Mechanical properties