A composite of titanium aluminide, reinforced with ZrO2 toughened Al2O3 fibers, has been produced by pressure casting. The stability of the microstructure during vacuum and air annealing was investigated by scanning and transmission electron microscopy (TEM). Processing resulted in partial dissolution of ZrO2 of the fiber into the molten metal which solidified into a two phase lamellar α2 + γ matrix. Vacuum annealing caused dissolution of Al2O3 fiber into the matrix, transformation of the matrix into γ and precipitation of ZrO2 and Al2Zr within γ. During air annealing diffusion of O through the fiber resulted in the formation of Al2O3 coated ZrO2 nodules extending from the fiber surface into the matrix in some regions and in the other regions the growth of Al2O3 into the γ of the lamellar matrix. An A15 phase with the metal composition, Ti3Al2, was found between the external oxide scale and the metal matrix.
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