From refined eutectic architecture to enhanced mechanical properties: Microstructure evolution and toughening behavior in SiC whisker-reinforced eutectic ceramics composites via hot-pressing

AbstractTo overcome the inherent low fracture toughness of sintered eutectic ceramics (SECs) and the intrinsic contradiction between sintering densification and eutectic lamellar coarsening, a novel SiC whisker (SiCw)-reinforced Al₂O₃/ZrO₂ eutectic composite with refined, coarsening-suppressed microstructure was fabricated via an integrated strategy of microstructural inheritance, whisker-mediated Zener pinning, and stepwise hot-pressing. Ultrafine eutectic powder (initial lamellar spacing λ = 0.224 μm) was blended with 5-15 vol% SiCw, whose aspect ratio distribution was statistically characterized and its toughening regulation was clarified. SiCw reduces sintering apparent activation energy by 23.4% to promote low-temperature densification, and inhibits lamellar coarsening via Zener pinning, verified by a 31.1% increase in coarsening activation energy and 16.5% reduction in Al₂O₃ grain size. With only 5 vol% SiCw, λ coarsening was limited to 8.9%, achieving a relative density of 98.73%, flexural strength of 565 MPa, and fracture toughness of 7.32 MPa m1/2 (SENB), a 61.6% improvement over unreinforced SECs. The non-monotonic property evolution is essentially dominated by competition among three microstructural regimes, with whisker pull-out contributing 54.6% of total toughening. This strategy enables high-performance large-scale SECs, while severe microstructural degradation after 1500 °C thermal exposure highlights critical high-temperature stability challenges.