Microstructure and mechanical properties of Al2O3/Y3Al5O12/ZrO2 hypereutectic directionally solidified ceramic prepared by laser floating zone

Al2O3/Y3Al5O12/ZrO2 directionally solidified ceramic has been considered as a promising candidate for ultrahigh temperature structural materials due to its excellent performance even close to its melting point. In this work, laser floating zone (LFZ) solidification experiments were performed on Al2O3/Y3Al5O12/ZrO2 hypereutectic with the solidification rates between 2 μm/s and 30 μm/s. The full eutectic lamellar microstructure is obtained with hypereutectic composition. The solid/liquid interface morphology is investigated. The microstructure characteristic is discussed based on the solid/liquid interface. The variation of lamellar spacing with different compositions and solidification rates was reported and discussed by considering an irregular eutectic growth model. The maximum hardness and fracture toughness are 19.06 GPa and 3.8 MPa m1/2, respectively. The toughening mechanism of ZrO2 is discussed based on the scenario of the crack propagation pattern.