Growth characteristic of Al2O3/Y3Al5O12 (YAG) eutectic ceramic in situ composites by laser rapid solidification

Directionally solidified ceramic eutectic in situ composite as a candidate for a high-temperature structural material has attracted considerable attention and various preparation techniques have been developed. In this study, pore-free eutectic ceramics of Al2O3/Y3Al5O12 (YAG) are prepared from melt by laser rapid solidification technique in order to investigate the microstructure characteristic and solidification behavior which are considered to be important factors influencing the properties of eutectic materials. The results show that: (1) The Al2O3/YAG eutectic displays a 'Chinese script' structure, and faceting is the most important factor to determine the formation of the irregular eutectic morphology. (2) The scanning rate and power density of the laser beam are the most primary technological parameters affecting the eutectic microstructure. The eutectic spacing is extremely fined due to the high-temperature gradient and solidification rate, and decreases with the increase of the scanning rate and the average is only around 1 μm. (3) Elongated colonies with the periodic distribution are observed in the solidified eutectic due to the high destabilization of solid-liquid interfaces caused by the ununiformity of the laser heat-flux distribution when the scanning rate is higher than 2000 μm/s