Orientation relationship formation in a uni-directionally solidified Al2O3/Ln(3)Al(5)O(12) (Ln = Y, Er) eutectic system

Formation of the orientation relationship for uni-directionally solidified Al2O3/Ln(3)Al(5)O(12) eutectic system at early stage of the solidification was examined. Ln(3)Al(5)O(12) was the first phase to nucleate in the Al2O3/ Ln(3)Al(5)O(12) eutectic microstructure. When the Ln(3)Al(5)O(12) phase nuc leated as the primary phase, no specific orientation for the Al2O3 and Ln(3 )Al(5)O(12) phases with respect to the solidification direction was formed, and the coupled eutectic growth occurs like polycrystalline. On the other hand, in the case of Al2O3 phase nucleated as the primary phase, a specific orientation for Al2O3 and/or Ln(3)Al(5)O(12) was easily formed. The orient ation relationship < 100 > (Al2O3) parallel to < 100 > Ln(3)Al(2)O(3) paral lel to < solidification direction > was obtained.