Phase Evaluation in Al2O3 Fiber-Reinforced Ti2AlC During Sintering in the 1300°C-1500°C Temperature Range.

In this article, the reactivity of Ti₂AlC powders, with 3 and 10 μm 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 1300°C were fully dense, with no apparent reaction between fiber and matrix. In samples HPed to 1500°C, even pure Ti₂AlC powders dissociated to Ti₃AlC₂ according to: 2 Ti₂AlC = Ti₃AlC₂ + TiAl _x ( l) + (1- x) Al ( l/ v), with x < 1. More severe Al loss results in the formation of TiC _y. 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 Ti₂AlC can be reinforced with Al₂O₃ fibers, the processing/use temperature will have to be kept below 1500°C, as, at that temperature the fibers, used here, sinter together. [ABSTRACT FROM AUTHOR]