Dresden 2009 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 37: Topical Session High Temperature Materials IV

MM 37.6: Vortrag

Donnerstag, 26. März 2009, 11:45–12:00, IFW A

Hot-Workability of Gamma-Based TiAl Alloys during Severe Deformation — •Ulrich Froebel — GKSS Research Centre, Institute for Materials Research, Max-Planck-Straße 1, D-21502 Geesthacht, Germany

Gamma-based titanium aluminides are intrinsically brittle up to relatively high temperatures. Inhomogeneous microstructures are particularly harmful in this respect, because critical values of constraint stress can develop after very small strains and lead to premature failure of the material. The structural and chemical homogeneity of components is hence extremely important for engineering applications and is most effectively accomplished by thermomechanical processing. The associated degree of microstructural transformation is determined by the imparted energy that triggers dynamic recrystallization. During traditional metal-forming processes such as extrusion and forging, the strain and thus the imparted energy, is inevitably limited due to geometrical constraints. This often leads to insufficient material consolidation, which is manifested by incomplete recrystallization and significant chemical inhomogeneity. Considerably increasing the deformation strain is therefore necessary to improve the homogeneity of components. In this context the feasibility of cyclic axial deformation, where the sample is deformed alternately in tension and compression or cyclic torsional deformation have been investigated. An assessment of the metallurgical potential of these techniques will be the subject of this presentation.