Rapid solidification behaviour of Al2O3/Y3Al5O12 (YAG) binary eutectic ceramic in situ composites

Rapid solidification of Al2O3/Y3Al5O12 (YAG) binary eutectic ceramic in situ composites during the remelting process using high-energy laser, which results in refinement of the solidification microstructure and improvement of the mechanical properties, is studied in this paper. The rapidly solidified Al2O3/YAG eutectic consists of Al2O3 and YAG phases without any other phases, effectively avoiding grain boundaries. The eutectic interspacing is extremely refined due to the high-temperature gradient and solidification rate of laser rapid solidification, and the minimal interspacing is as fine as 0.5 μm. The eutectic exhibits an obvious faceted–faceted eutectic growth characteristic which mainly derives from the high-fusion entropies of eutectic phases and large kinetic undercooling. The mean hardness and fracture toughness measured by an indentation technique are 17.5 GPa and 3.6 MPa m1/2, respectively. The increase of fracture toughness can be attributed to the refinement of eutectic phases which restrain and arrest crack propagations.