Ultra-high strength micro-nano quasi-monocrystalline Al₂O₃/Y₃Al₅O₁₂/ZrO₂ ternary eutectic ceramics processed by high-speed directional solidification

A micro-nanostructured Al₂O₃/YAG/ZrO₂ eutectic ceramic containing quasi-monocrystalline Al₂O₃ and Y₃Al₅O₁₂ (YAG) phases was fabricated via high-rate directional solidification at a pulling rate of 100 μm/s. Despite a cellular solidification interface, the two phases grew along specific crystallographic orientations, forming a homogeneous and refined eutectic microstructure. The resulting rod-shaped composites exhibited a large diameter of up to 3.5 mm and an ultra-high flexural strength of 2.5 GPa. The stable directional solidification process and high temperature gradient played a key role in enabling continuous growth of micro-nano quasi-monocrystalline phases under such a high pulling rate. These quasi-monocrystalline phases minimized grain boundary defects and significantly restricted microcrack propagation within the specimens. The effective control of defects ultimately contributed to the exceptional flexural strength. This study highlights the potential of high-speed directional solidification technology for preparing high-performance composite ceramics.