Microstructure of Al ₂ O ₃ –8YSZ eutectic ceramics formed via flash event at various furnace temperatures

Abstract In the present study, Al 2 O 3 –8 mol% Y 2 O 3 ‐stabilized ZrO 2 (8YSZ) eutectic ceramics with refined microstructure were produced by using a flash event at various furnace temperatures, and the effect of cooling rate during solidification on the eutectic microstructure was examined. Calcined bodies of Al 2 O 3 and 8YSZ at the eutectic composition were subjected to local melting and subsequent rapid solidification by flash events using alternating current electric fields at different furnace temperatures in a range of 600°C‒1400°C, which were remarkably below the eutectic point of 1870°C. The eutectic microstructure was refined with the increasing cooling rate; the greater the difference between the furnace and specimen temperatures during a flash event, the faster the cooling rate was achieved. The interphase spacing of 135 ±11 nm, which was comparable with the finest Al 2 O 3 –ZrO 2 eutectic in the literature, was obtained at the lowest furnace temperature of 600°C. Rod‐like microstructures with YSZ rods aligned in Al 2 O 3 single crystal matrix were formed at lower cooling rates, while lamellar microstructures were formed at higher cooling rates. The rod–lamellar transition in the present materials was explained by the coupled growth theory of eutectic materials.