There are two eutectic systems in the Al2O3-Y2O3 system: one is the Al2O3-YAG equilibrium eutectic system and the other is the Al2O3-YAP metastable eutectic system. Heating the Al2O3-YAP metastable eutectic structure up to temperatures above the metastable eutectic temperature but below the equilibrium eutectic temperature produced the undercooled melt. Solidification in the equilibrium path immediately followed the undercooled melt formation. The solidification in the equilibrium path along with the melting of the metastable eutectic structure resulted in a fine and uniform equilibrium eutectic structure. This paper demonstrates the shape casting by using the undercooled melt formation.