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

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 n-dcrostructural refining effect of C and Y, mainly contributed to the strength at room temperature as well as at high temperature up to 800degreesC, 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 alpha(2) and gamma phases. Plastic deformation of gamma plates during tensile testing occurred through the activation of ordinary dislocations of perfect Burger's vectors. In an oxidation test in air, the Y-containing alloys showed a significantly low weight gain compared with the Y-free alloy. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.