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

The eutectic Al2O3/Y3Al5O12 with the dimension of 150 mm x 90 mm x 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) over bar 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.