Rapid fabrication of bulk graded Al2O3/YAG/YSZ eutectics by combustion synthesis under ultra-high-gravity field

A rapid and simple way of producing bulk graded Al2O3/YAG/YSZ ternary eutectics was investigated. The combustion reaction between Al/Fe2O3/Y2O3/ZrO2 led to the formation of molten mixtures consisting of Al2O3/YAG/YSZ, and the subsequent separation of the ceramic melt from the iron melt was realized under ultra-high-gravity field, followed by the solidification of the ceramic melt. The as-solidified ceramic ingot sank into the iron melt, where an instantaneous isostatic pressure about 2 MPa was exerted on the around of the ceramic ingot resulting in an enhanced degree of densification. Microstructure analysis demonstrated that densified ceramic was composed of Al2O3/YAG/YSZ ternary eutectics. The phase composition, morphologies, hardness and fracture toughness of the eutectic product changed gradually along the direction of high gravity field. The maximum density of the eutectic ceramic was 97.32%, correspondingly, the maximum value of the Vickers hardness and fracture toughness reached 17.82 GPa and 5.51 MPa m1/2, respectively.