Isotropy in large-size Al₂O₃/Y₃Al₅O₁₂ eutectic ceramic grown by Horizontal Directional Solidification method

The eutectic Al₂O₃/Y₃Al₅O₁₂ with the dimension of 150 mm×90 mm×20 mm was grown in vacuum by Horizontal Directional Solidification (HDS) method. The thermal and mechanical properties were investigated from room temperature to 1273 K, on specimens whose longitudinal directions were parallel (L-specimen) and perpendicular (T-specimen) to the solidification direction. Even though new preferred orientations of (1 1 2¯ 3) Al₂O₃ and (5 3 2) Y₃Al₅O₁₂ emerged in L-specimen, neither in T-specimen, isotropic properties of residual stresses in Al₂O₃ phase, thermal expansion coefficients, flexural and compressive strengths appeared. For HDS-Al₂O₃/Y₃Al₅O₁₂, the reasons of improved Vickers hardness were discussed.