One-step additive manufacturing and microstructure evolution of melt-grown Al₂O₃/GdAlO₃/ZrO₂ eutectic ceramics by laser directed energy deposition

Synchronized-powder-feeding-based laser directed energy deposition (LDED) has great application potential for the rapid fabrication of large-scale composite ceramics with complex shapes. In this study, near-full-density Al₂O₃/GdAlO₃/ZrO₂ ternary eutectic ceramics with different shapes and smooth surfaces were directly prepared by using an improved LDED device. Spherical ceramic powders with eutectic composition and good flowability were obtained by centrifugal spray drying. The microstructure characteristics and microstructure evolution of the rapidly solidified 3D-printed eutectic ceramic were systematically elucidated. In particular, the formation mechanism of the observed periodic banded structures was revealed through a unique laser partial remelting technique. The result indicated that the appearance of the banded structure is attributed to the drastic abnormal coarsening of the nanoscale microstructures adjacent to the molten pool. On the basis these results, a physical model was proposed to illustrate the microstructure evolution of the 3D-printed Al₂O₃/GdAlO₃/ZrO₂ eutectic ceramic.