Processing, microstructure, and properties of laser remelted Al₂O₃/Y₃Al₅O₁₂(YAG) eutectic in situ composite

Laser remelting and rapid solidification were performed in preparing the high-performance Al₂O₃/Y₃Al₅O₁₂(YAG) eutectic in situ composite. The microstructure characteristic and solidification behavior were studied using scanning electron microscopy (SEM), energy dispersive spectroscopy(EDS), X-ray diffractometry(XRD) and simultaneous thermal analysis(STA). The hardness and fracture toughness were obtained using an indentation technique. The results show that the laser remelted Al₂O₃/YAG composite has a homogeneous eutectic microstructure without microcrack and pore. The component phases of Al₂O₃ and YAG are three-dimensionally and continuously reticular connected, and finely coupled without grain boundaries, colonies and amorphous phases between interfaces. The eutectic interspacing is greatly refined with increasing the scanning rate and average is only 1 μm. The synthetically thermal analysis indicates that the eutectic temperature of Al₂O₃-YAG is 1 824 °C, well matching the phase diagram of Al₂O₃-Y₂O₃ system. The maximum hardness reaches 19.5 GPa and the room fracture toughness is 3.6 MPa.m^1/2.