Phase Evaluation in Al2O3 Fiber-Reinforced Ti2AlC During Sintering in the 1300 degrees C-1500 degrees C Temperature Range
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In this article, the reactivity of Ti2AlC powders, with 3 and 10 m alumina, Al2O3, fibers during pressure-assisted sintering is explored. Samples were fabricated by hot-isostatic-pressing (HIPed) or hot-pressing (HPed), and characterized by X-ray diffraction, differential thermal analysis, and electron microscopy-both scanning and transmission- equipped with energy dispersive X-ray spectroscopes. Samples prepared at 1300C were fully dense, with no apparent reaction between fiber and matrix. In samples HPed to 1500C, even pure Ti2AlC powders dissociated to Ti3AlC2 according to: 2 Ti2AlC = Ti 3AlC2 + TiAlx (l) + (1-x) Al (l/v), with x < 1. More severe Al loss results in the formation of TiCy. The presence of the Al2O3 fibers delayed densification enough to allow most of the Al and some of the Ti to escape into the vacuum of the hot press or react with the encapsulating glass during HIPing a resulting in a more intensive dissociation of the Ti2AlC. Although, in principle Ti 2AlC can be reinforced with Al2O3 fibers, the processing/use temperature will have to be kept below 1500C, as, at that temperature the fibers, used here, sinter together. 2011 The American Ceramic Society.
