In Situ Construction of Hierarchical Microstructures for Highly Tough ZrC Multiphase Ceramics at Reduced Temperatures

A hierarchical microstructural design strategy is proposed to enhance the sinterability and fracture toughness of ZrC ceramics via in situ reactions between TiSi 2 and B 4 C. (Zr,Ti)C–(Ti,Zr)B 2 –SiC multiphase ceramics were fabricated by reactive hot pressing at 1600°C. During sintering, TiSi 2 and B 4 C preferentially react to yield platelet‐like (Ti,Zr)B 2 and primary SiC, while liberated Si reacts with the ZrC matrix to precipitate secondary SiC. Crucially, B 4 C incorporation suppresses excessive carbon depletion from the ZrC matrix, mitigating carbon vacancy formation. The optimal composite features an interconnected grain boundary network of (Ti,Zr)B 2 –SiC aggregates, refining matrix grains to 0.54 µm. Tailored interfacial features, including semicoherent boundaries and interdiffusion layers, provide a robust foundation for efficient stress transfer. Driven by solid‐solution strengthening, grain refinement, multiscale SiC pinning, and crack deflection/bridging by plate‐like (Ti,Zr)B 2 , the composite achieves an improved flexural strength of 545 MPa and a fracture toughness of 7.7 MPa·m 1/2 . This strategy successfully couples low‐temperature densification with synergistic toughening for advanced refractory carbides.