Microstructural characterization of a zirconia-toughened alumina fiber reinforced niobium aluminide composite

This paper reports on an NbAl3 + Nb2Al composite reinforced with continuous zirconia-toughened alumina, PRD-166 fibers, that was produced by pressure casing and was examined by optical and transmission electron microscopy and energy dispersive spectroscopy. Exposure of the fiber to the molten metal resulted in ZrO2 and Al;2O3 grain growth, formation of a thin layer of an amorphous phase on the grain boundaries of Al2O3 and transformation of ZrO2. Preferential Al2O3 grain growth near the surface of the fiber led to the rejection of ZrO2 from this region into the molten metal. In NbAl3 slip occurred by the glide of a left-angle 110 right-angle superdislocations and to a lesser extent by the glide of a pair of left-angle 11 bar 1 right-angle + left-angle 3 bar 1 bar 1 right-angle dislocations on the (112) planes and a/2 left-angle 110 right-angle superpartial dislocations on the (001) plane. The operating slip system in Nb2Al was identified as {010 left-angle 100 right-angle. A left-angle 100 right-angle dislocations were dissociated into a/x left-angle 100 right-angle partial dislocations joined together by a stacking fault