Abstract
Directionally solidified Al2O3/Er3Al5O12 (EAG) eutectic ceramic was prepared via vertical Bridgman method with high-frequency induction heating. The effects of the growth rate on the microstructure and mechanical properties of the solidified ceramic were investigated. The experimental results showed that there were no pores or amorphous phases in the directionally solidified Al2O3/EAG eutectic ceramic. Al2O3 phase was embedded in the EAG matrix phase, and the two phases were intertwined with each other to form a typical binary eutectic “hieroglyphic” structure. With the increase of growth rate, the phase size and spacing of the solidified Al2O3/EAG ceramic both decreased, and the growth rate and phase spacing satisfied the λ2v ≈ 60 formula of Jackson-Hunt theory. The cross section microstructure of the solidified ceramic always exhibited an irregular eutectic growth, while the longitudinal section microstructure presented a directional growth. The mechanical properties of the solidified ceramic gradually increased with the increase of growth rate, and the maximum hardness and fracture toughness could reach 21.57 GPa and 2.98 MPa·m1/2 respectively. It was considered that the crack deflection and branching could enhance the toughness of the solidified ceramic effectively.
Highlights
In recent years, the aerospace industry has put forward more stringent requirements on the high-temperature performance and safety of aircraft engine core components
Directionally solidified Al2 O3 /Er3 Al5 O12 (EAG) eutectic ceramic was prepared via vertical Bridgman method with high-frequency induction heating, which provided a large solid-liquid interface temperature gradient and a high growth rate for the eutectic growth
The sintered ceramic was composed of polycrystalline grains, which contain pores and grain boundaries
Summary
The aerospace industry has put forward more stringent requirements on the high-temperature performance and safety of aircraft engine core components (turbine blades and the like). Nickel-based and cobalt-based single crystal alloys are the most widely used turbine blade materials in the aerospace field, of which the highest working temperature can be up to 1100 ◦ C Their mechanical properties above 1100 ◦ C will be significantly degraded [1], and their high temperature stability and safety cannot meet the aviation needs. Sayir [7] reported a promising ultra-high temperature material—Al2 O3 /EAG oxide eutectic composite ceramic, which has great potential for long-term operation in a high temperature environment above 1600 ◦ C [7,8,9]. Directionally solidified Al2 O3 /Er3 Al5 O12 (EAG) eutectic ceramic was prepared via vertical Bridgman method with high-frequency induction heating, which provided a large solid-liquid interface temperature gradient and a high growth rate for the eutectic growth. The effects of growth rate (v, 0–24 mm/h) on the microstructure and mechanical properties of Al2 O3 /EAG eutectic ceramic were investigated
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