Improvement of cyclic oxidation resistance of Y-containing TiAl-based alloys with equiaxial gamma microstructures

The cyclic oxidation behavior of Y-containing TiAl-based alloys was studied by oxidation kinetic curves and microstructural modification of the scale. Oxidation resistance of the experimental alloys in synthetic air at 800 °C was improved by Y-addition. The Y-addition was very effective in improvement of the adhesion between scale and alloy due to decrease in thickness of the scale. Diffusion of oxygen and the growth of the oxide grains were strongly impeded by the precipitation of Y2O3 at oxide grain boundaries in the scale which was confirmed by the TEM observation. The excellent oxidation resistance obtained in the Y-containing alloys was mainly attributable to the formation of a continuous Al2O3 scale in the outer layer by retarding inward diffusion of oxygen.