Effect of seed orientations on crystallographic texture control in faceted Al2O3/YAG eutectic ceramic during directional solidification

Abstract

Crystallographic texture control is a major challenge in directionally solidified multiphase eutectic ceramics with complex faceted growth characteristics. In this study, the Czochralski (CZ) technique is proposed to prepare eutectic single crystal ceramic with large size (Φ 30 mm × 125 mm). A highly oriented and unique texture of Al2O3/Y3Al5O12 (YAG) eutectic ceramic is formed via the 〈112¯0〉 Al2O3 single crystal seed induction based on crystallographic orientation tailoring. The orientations of Al2O3/YAG eutectic are more strictly constrained by single crystal seed induction on the basis of the minimum interface energy principle, resulting in a defined single orientation relationship along the solidification direction. In particular, the single crystallographic orientation can be obtained in a short competitive solidification distance under the influence of epitaxial solidification from single crystal seed. Therefore, it has been confirmed that the orientations of 〈112¯0〉Al2O3 and 〈111〉 YAG are preferentially stabilized with the minimum under-cooling during directional solidification. Crystallographic orientation disturbances and instabilities due to polycrystalline crystal seed are avoided. Finally, the successful texture control inducted by 〈112¯0〉 Al2O3 single crystal seed can provide a promising orientation design pathway for faced oxide eutectic solidification.