Microstructure refinement approaches of melt-grown Al2O3/YAG/ZrO2 eutectic bulk

Microstructure developments of melt-grown Al2O3/YAG/ZrO2 ceramic bulks were investigated by controlling composition, cooling rate, heterogeneous nucleation sites and melt superheating treatment. The solidification microstructure of sample with hypereutectic composition (ZrO2 20 mol%) is finer than that with hypoeutectic or eutectic ones. With increasing the cooling rate, microstructure of melt-grown samples develops from colony to dendrite and finally to cell. The microscopy and the components of samples vary with the melt superheating temperature and the type of heterogeneous nucleation sites. The microstructure evolutions of melt-grown Al2O3/YAG/ZrO2 eutectic relate to the melt undercooling level and the solid–liquid interfaces stability.