Hamburg 2001 – wissenschaftliches Programm

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M: Metallphysik

M 24: Intermetallische Phasen II

M 24.5: Fachvortrag

Mittwoch, 28. März 2001, 18:15–18:30, S5.3

Work hardening characteristics of gamma based titanium aluminides — •Jonathan Paul and Fritz Appel — GKSS Forschungzentrum Geesthacht GmbH, Max-Planck-Str., 21502 Geesthacht

Extensive investigations of structure/property relationships have led to a detailed database of the mechanical properties of titanium aluminides. A topic that has received far less attention is the effect of work hardening. This is certainly in part due to the high brittleness of TiAl alloys, which persists to test temperatures in excess of 700 C and limits tensile ductility. However, in compression it is possible to produce work hardening over large plastic strains and a wide range of temperatures, which apparently provide a significant potential to strengthen the material.

The work hardening mechanisms will be characterised in terms of glide obstacles and the velocity and slip path of dislocations. The effect of temperature and strain rate on the flow stress was studied in order to describe the work hardening behaviour in terms of activation volumes and activation energies. The mechanical tests were supplemented by electron microscope observations of the defect structure involving high-resolution and in-situ techniques. The thermal stability of the deformation induced defect structure was assessed by isothermal and isochronal annealing.