In-situ architecting of reinforcing/toughening units in (Ti,W)C composites via two-step reactive SPS for enhanced strength and toughness

This study proposes a novel in-situ microstructural architecting strategy by introducing ZrSi₂ and B₄C as reactive precursors via a two-step reactive spark plasma sintering (SPS) process. Leveraging the low melting point of ZrSi₂, a transient liquid phase initiates rapid densification and primary reactions at 1600 °C, followed by controlled secondary solid-liquid reactions at 1800 °C. This cascade reaction pathway successfully constructs a hierarchical reinforcement system comprising nano-scale SiC particles, sub-micron plate-like TiB₂/W₂B₅, and WSi₂/SiC agglomerates, accompanied by extensive multicomponent solid solution formation. Consequently, the optimized composite achieves near-full densification (>99%) and exceptional mechanical properties, exhibiting a flexural strength of 882 MPa and a fracture toughness of 7.4 MPa·m^1/2. The enhancement stems from multiscale coupling: atomic-scale solid solution strengthening, nano-scale SiC pinning, and micro-scale crack deflection/bridging by plate-like grains. This approach offers a viable design route for high-performance refractory carbides in extreme environments.