We have studied the effect of melt quenching in the solidification behavior of ternary composites, for the Al2O3-Y3Al5O12 (YAG)-ZrO2 subsystem inside the ternary oxide system Al2O3-Y2O3-ZrO2. Ternary composites were prepared by melting and rapid quenching, in air, in an are-image furnace. Solid phases were studied by XRD and Raman spectroscopy. Mutual substitution of the different cations in the solid phases is promoted by the rapid phase separation during quenching. The Al2O3-YAG-ZrO2 subsolidus region in the ternary diagram was determined for are-image rapidly solidified composites.