Fabrication and characterization of Al ₂O ₃/Y ₃Al ₅O ₁₂ eutectic in situ composite ceramics by double side laser zone remelting method

Al ₂O ₃/YAG eutectic in situ composite ceramics were prepared by double side laser zone remelting (DSLZR) with aiming at investigating the melting and solidification rules of oxide eutectic ceramics with large size under DSLZR condition. The solidification microstructures were characterized by SEM, XRD and EDS. The results show that solidified layer thickness of eutectic ceramics is enhanced by DSLZR. The eutectic ceramic plates with density up to 98.5%±1% are obtained, in which the thickness is 8.2 mm, and the length is 65.0 mm. The thickness of solidified layer is increased with decreasing laser scanning rate and increasing laser power. The density is initially increased and then decreased with the increase of laser scanning rate. The eutectic ceramic obtained by DSLZR is only consisted of uniform and interweaved Al ₂O ₃ and YAG phases. The relation between the eutectic spacing (λ; only 1.0~3.5 μm) and solidification rate (v) agrees with the Jackson-Hunt formula. With the increase of laser scanning rate, the eutectic spacing reduces. Furthermore, the growth of eutectic at double side remelting interface is continuous, so the binded interface is very well. The eutectic ceramic obtained has high Vickers hardness ((18.6±1.0) GPa) due to the fine solidification microstructure.