Effect of cooling rate on the microstructure and mechanical properties of melt-grown Al2O3/YAG/ZrO2 eutectic ceramic

Melt-grown Al2O3/YAG/ZrO2 ternary eutectic samples were solidified by quenching and with controlled cooling rates of 10, 50, and 250 °C/min, respectively. Effect of cooling rate on microstructure and mechanical properties were examined. With the increase of cooling rate, three classical characteristic microstructures are obtained and developed from colony structure to dendrite structure and to cell structure. In the quenching process, the sample consists of lamellar eutectic cells and its fracture toughness increases to 4.13 ± 0.8 MPa m1/2. The microstructure transitions with the cooling rate are attributed to instability of the solid–liquid interface. In this work, the interface instability is analyzed to explain the microstructure evolutions in terms of undercooling and characteristic lengths of solute diffusion and capillarity effect.