Abstract
The cyclic oxidation behaviour of intermetallic Ti-46Al-8Ta (at.%) alloy was studied in the air. Long-term oxidation experiments were carried out on the samples with convoluted type of &gama;(TiAl) + α₂ (Ti₃Al) microstructure at temperatures ranging from 700 to 800 °C for oxidation time up to 3100 h. The oxidation kinetics was determined from the weight gain measurements as a function of oxidation time and temperature. The parabolic rate constants and activation energy for oxidation were calculated and discussed. The experimental results showed that the spallation had no significant effect on oxidation kinetic curves at 700 and 760 °C up to 3100 h but affected the measured kinetics at 800 °C for oxidation time longer than 500 h. The EDS and X-ray diffraction observations showed that the scales consisted of TiO₂, α-Al₂O₃, Ti₂AlN, TaAlTi and TiN phases.

Key words
titanium aluminides, TiAl, cyclic oxidation, microstructure

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