Stability of crystallographic texture and mechanical anisotropy toward Al₂O₃/YAG eutectic ceramic composite using single crystalline seeds

During the directional solidification of Al₂O₃-based eutectic ceramic composites, crystallographic orientation control is a promising method for tailoring the performances of composite parts. However, despite its importance in the fabrication of texture-controlled structural parts, the stable growth of the eutectic crystallographic texture for long distance (growth distance from 30 mm to 120 mm) in ceramic composite system is not widely understood. Herein, the competition and stability of crystallographic texture for Al₂O₃/YAG eutectic ceramic composite induced by different seeds using the Czochralski (CZ) technique were investigated. When the eutectic composites induced by different single crystalline Al₂O₃ seeds, coarse Al₂O₃ particles and uniform eutectic structure appeared alternately below the seeds. While the eutectic ceramic composite induced by YAG seed has a memory effect on the stability of its microstructure and morphology. We demonstrated that the eutectic ceramic composites induced by the ⟨112‾0⟩ Al₂O₃ and ⟨101‾0⟩ Al₂O₃ seeds could stably inherit the seed orientation and grow as a single crystallographic texture with a low interfacial strain (<10 %). In particular, the stable evolution of crystallographic texture depended not only on the type of seeds but also on the mutual constraint of eutectic coupling growth. Furthermore, the nano-hardness, elastic modulus, and compressive strength (1600 °C) of the composites induced by different seeds have anisotropic characteristics. However, the bending strength was not sensitive to the change of crystallographic texture. It could maintain excellent high temperature stability, which was approximately 265–316 MPa from room temperature to 1600 °C. These results promote the development of high-performance Al₂O₃-based eutectic ceramic composites with anisotropic design using seeding technique to tailor their crystallographic texture.