Microstructural refinement and improvement of mechanical properties and oxidation resistance in EPM TiAl-based intermetallics with yttrium addition Original Research Article

New Y-modified TiAl-based alloys, with nominal chemical compositions of Ti–46.6Al–1.4Mn–2Mo–0.3C–xY (x=0.1, 0.33 and 0.6), were developed with the elemental powder metallurgy (EPM) method. The alloys with Y addition had higher ultimate tensile strength, elongation and oxidation resistance than the Y-free alloy. Combined solid-solution strengthening of Mn, Mo, C and Y, and the microstructural refining effect of C and Y, mainly contributed to the strength at room temperature as well as at high temperature up to 800°C, in addition to strengthening due to Y2O3 and carbide precipitation. The room-temperature ductility was also improved by the microstructural refinement and the removal of interstitial oxygen in the α2 and γ phases. Plastic deformation of γ plates during tensile testing occurred through the activation of ordinary dislocations of perfect Burgerʹs vectors. In an oxidation test in air, the Y-containing alloys showed a significantly low weight gain compared with the Y-free alloy.