Texture control and high-temperature strength of directionally solidified Al₂O₃/YAG/ZrO₂ eutectic composite rods

A₂O₃/YAG/ZrO₂ eutectic Melt-Growth-Composite (MGC) rods with two different microstructures were prepared by unidirectional solidification using the modified-pulling-down method (MPD) under different processing parameters. Microstructure and crystallographic texture were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and electron backscattered pattern (EBSP) method. High-temperature strength was evaluated by compression tests at 1773 K and 1873 K. Geometric pattern structure and Chinese script pattern structure are evolved by controlling processing parameters. MPD rods have strong preferred growing orientations in Al₂O₃ of (001) for the geometric pattern structure and of (300) for Chinese script pattern structure. Constituent phases in the MPD rod hold the orientation relationship. The yield stress for the geometric pattern structure is over 1 GPa at 1773 K, which is extremely higher than that for Chinese script pattern structure. High-temperature strength at 1773 K and 1873 K depends on strain rate and temperature in both the MPD rods.