| The oxidation kinetics and morphological changes of oxides in intermetallic compound TiAl containing 37wt% Al have been investigated in air over the temperature range of 973K to 1473K. The phases of oxidation products have been examined by X-ray diffractometer and scanning electron microscope. They are composed of four layers, that is, TiO₂, Al₂O₃, TiO₂+Al₂O₃, Ti₃Al from the outer layer. The mass gain during the oxidation increases rapidly at temperatures above 1173K, obeying the parabolic law. The oxidation resistance is related to the characteristics of a protective oxide layer(Al₂O₃, or TiO ₂). The existance of the Al₂O₃ layer has improved oxidation resistance of TiAl. However, this Al₂O₃ layer is not dense enough to prevent the oxidation above 1173K. The growth rate of TiO₂ is faster than that of Al₂O₃ at high temperature. Oxidation rate of TiAl is controlled by titania-forming kinetics above 1273K but controlled by alumina-forming kinetics below 1173K. |
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