Fabrication of Al2O3–YAG Equilibrium Eutectic Composites via Transformation from Fine Al2O3 and YAP Powder Mixtures

A process for the fabrication of Al2O3­YAG eutectic composites using an undercooled melt formed by the melting of an Al2O3­YAP eutectic specimen has been developed. An Al2O3­YAG eutectic structure with fine lamellar spacing was formed. However, the Al2O3­YAG casting has porosities with diameters of 4­9μm. The composition is limited to the Al2O3­YAP eutectic composition. In this paper, a new method for the fabrication of Al2O3­YAG eutectic composites through the transformation from fine Al2O3 and YAP powder mixtures is proposed. The enhancement of YAG formation due to the fine Al2O3 and YAP powders and the 11% volume expansion in the transformation from the Al2O3­ YAP system to the Al2O3­YAG system contributed to the formation of dense Al2O3­YAG eutectic compact. The Al2O3­YAG compact featured a uniform microstructure consisting of spherical-like Al2O3 and YAG grains. In addition, the forming temperature was reduced to 1873K, which is approximately 100K lower than that in the previous process using the undercooled melt. The proposed process provides a dense Al2O3­YAG eutectic compact with a fine and uniform microstructure over a wide composition range of Al2O3­xmol%Y2O3 (10 < x < 30). [doi:10.2320/matertrans.M2012047]