Growth characteristics of directionally solidified Al2O3/YAG/ZrO2 ternary hypereutectic in situ composites under ultra-high temperature gradient

Abstract

Oxide eutectic ceramic in situ composites have attracted significant interest in the application of high-temperature structural materials because of their excellent high-temperature strength, oxidation and creep resistance, as well as outstanding microstructural stability. The directionally solidified ternary Al2O3/YAG/ZrO2 hypereutectic in situ composite was successfully prepared by a laser zone remelting method, aiming to investigate the growth characteristic under ultra-high temperature gradient. The microstructures and phase composition of the as-solidified hypereutectic were characterized by using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The results show that the composite presents a typical hypereutectic lamellar microstructure consisting of fine Al2O3 and YAG phases, and the enriched ZrO2 phases with smaller sizes are randomly distributed at the Al2O3/YAG interface and in Al2O3 phases. Laser power and scanning rate strongly affect the sample quality and microstructure characteristic. Additionally, coarse colony microstructures were also observed, and their formation and the effect of temperature gradient on the microstructure were discussed.