The effect of yttrium on microstructure and dislocation behavior of elemental powder metallurgy processed TiAl-based intermetallics

The effect of yttrium on microstructure and mechanical properties of elemental powder metallurgy (EPM) processed TiAl-based alloys was studied. Y-addition, by forming Y2O3 through internal oxidation, improved tensile yield strength of TiAl-Mn-Mo-C alloys based on microstructural refinement and precipitation hardening. The tensile ductility of the alloys was also improved moderated by Y-addition, which was attributed to scavenging of oxygen and activation of ordinary 1/2 < 110] type dislocations. A profuse generation of the dislocations ahead of the crack tip was also confirmed by an in situ TEM experiment. Y-addition did not seriously affect the cracking characteristics of alloys except for the enlarging plastic zone (PZ) size near the crack tip. (C) 2004 Published by Elsevier B.V.