Formation of Al 2 O 3 –GdAlO 3 eutectic ceramics with a fine anisotropic structure in a flash event

Abstract An Al 2 O 3 –GdAlO 3 (GAP) composite with a fine eutectic microstructure was obtained through local melting and rapid solidification during a flash event. An AC field of 1 kV/cm at a frequency of 1 kHz was applied to a calcined Al 2 O 3 –GAP body at a furnace temperature of 1400°C to induce the flash event. The Al 2 O 3 –GAP body exhibited local melting through the current path. Solidification proceeded with the maximum cooling rate of about 140°C/s just after the power supply was turned off. Using this flash treatment, a refined eutectic structure with rodlike GAP phases in the Al 2 O 3 matrix was obtained within 1 min. The interphase spacing of the obtained structure was approximately 170 nm, comparable with the finest Al 2 O 3 –GAP eutectic material obtained in previous studies. A flash event and subsequent rapid cooling can contribute to forming fine eutectic ceramics with a relatively low furnace temperature and short processing time.