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In this article, toughness, oxidation, and rupture behaviors of present-generation refractory metal-intermetallic composites are compared to the performance requisites necessary to make these materials a competitive choice for the jet engine turbine environment of the future.

The tensile properties of the intermetallic compound TiAl have been determined at several temperatures in the range 25 to 1000°C. Additional variables studied were the influence of strain rate and the effect of exposure to oxidizing conditions prior to testing. The modes of deformation under the various testing conditions were studied in the electron microscope, the modes of fracture were studied in the scanning electron microscope, and these data were correlated with the mechanical properties. The results indicate that the ductilebrittle transition behavior of TiAl at about 700°C is controlled by the trailing a/6 [112] partial dislocation components of the a [011] superdislocations overcoming their pinning barriers. It was also shown that prior exposure to oxidizing conditions does not markedly influence the mechanical properties of TiA1.

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