Theoretical prediction and experimental comparison for eutectic growth of Al₂O₃/GdAlO₃ faceted eutectics

Ultra-fine Al₂O₃/GdAlO₃ eutectics with eutectic spacing of 193 ± 20 nm are directionally solidified by laser floating zone melting process. When the solidification rate increases from 2 μm/s to 400 μm/s, the morphology transition from “Chinese script” irregular eutectic to rod-like regular eutectic is found. To predict the growth behaviour of Al₂O₃/GdAlO₃ eutectic, the solute diffusion coefficient D_L, which exhibits significant influence on eutectic growth, is determined to be 6 × 10⁻¹⁰ m²/s. Then, the eutectic microstructures as a function of solidification rate are well predicted by modified Magnin-Kurz model and Jackson-Hunt model, both for “Chinese script” irregular eutectic and rod-like regular eutectic, respectively.