Preparation and characterization of Al{sub 2}O{sub 3}/Y{sub 3}Al{sub 5}O{sub 12}/ZrO{sub 2} ternary hypoeutectic in situ composites by laser rapid solidification
- State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072 (China)
The directionally solidified oxide eutectic in situ composite is one of the most promising high-temperature structural materials in oxidizing environments. Pore-free rods and plates of ternary Al{sub 2}O{sub 3}/Y{sub 3}Al{sub 5}O{sub 12} (YAG)/ZrO{sub 2} hypoeutectic in situ composites with hypoeutectic composition (71 mol % Al{sub 2}O{sub 3}, 17 mol % Y{sub 2}O{sub 3}, and 12 mol % ZrO{sub 2}) are prepared rapidly by the laser zone remelting technique. The hypoeutectic growth and microstructure characteristic of grown crystals are studied using the scanning electron microscopy, x-ray diffraction, and energy dispersive spectroscopy, aiming to understand well the rapid solidification behavior of the ternary oxide system of Al{sub 2}O{sub 3}-Y{sub 2}O{sub 3}-ZrO{sub 2}. The rapidly solidified Al{sub 2}O{sub 3}/YAG/ZrO{sub 2} hypoeutectic shows a refined, interpenetrating, and irregular lamellar structure with a reticular distribution of coarse Al{sub 2}O{sub 3} and yttrium aluminum garnet (YAG) and smaller ZrO{sub 2} phases. The fine ZrO{sub 2} phases are partially embedded at the Al{sub 2}O{sub 3}/YAG interfaces. Moreover, the typical dendrite microstructure similar to the metallic solidification is also observed. The formation of two kinds of microstructures is mainly attributed to the rapid growth during the laser zone remelting and constitutional supercooling. The Al{sub 2}O{sub 3} and YAG phases grow in a typical faceted manner, and the ZrO{sub 2} phase presents a weak-faceted growth. The size of the interphase spacing obtained decreases rapidly in increasing the laser scanning rate. The fundamental investigations on the irregular growth mechanisms of the hypoeutectic are suggestive to the comprehension of the complex solidification behavior of the ternary oxide systems.
- OSTI ID:
- 21137399
- Journal Information:
- Journal of Applied Physics, Vol. 104, Issue 2; Other Information: DOI: 10.1063/1.2955768; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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