Stabilization of zirconia lamellae in rapidly solidified alumina-zirconia eutectic composites

In-situ fabrication of ceramic eutectic composites by rapid solidification of eutectic drops is a cheap and quick method compared to directional solidification or to multi-step fabrication methods of fiber reinforced/layered materials for high temperature use. Binary eutectic composites with a homogeneous periodic microstructure have been obtained by directional solidification of eutectic melts for many years, but typical solidification velocities used in directional solidification are limited to the range of cm/hour or, more recently, up to 15 mm/min. The present study aims to determine the effects of faster solidification rates on the structure of the alumina-zirconia binary composites obtained at higher growth rates by rapid solidification from eutectic melts in air or vacuum. A binary composite with zirconia stabilized in the high-temperature tetragonal form is presented. The stabilization of the tetragonal phase has not been observed before in bulk crystalline pellets of binary Al2O3-ZrO2 eutectic composites.