Regensburg 2002 – scientific programme

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M: Metallphysik

M 29: Intermetallische Phasen III

M 29.2: Fachvortrag

Friday, March 15, 2002, 11:45–12:00, H6

TiAl component strength - influence of work hardening stability — •Jonathan Paul and Appel Fritz — GKSS Forschungszentrum, Max-Planck-Strasse, D-21502 Geesthacht, Germany

This paper studies the origin and thermal stability of the defects that give rise to work hardening during room temperature deformation. The investigations involve mechanical testing, electron microscope observations of the defect structure, and recovery experiments. The investigations indicate that work hardening is derived from long-range elastic interactions between dislocations on parallel and oblique slip planes. Another source of work hardening arises from dislocation dipoles and debris defects, which were trailed and terminated at jogs in screw dislocations. Removal of these defects through annealing gives rise to a significant recovery of the work hardening. Thus, most of the room temperature work hardening is lost after just a few hours exposure to operating temperatures (700-750 degrees C). A novel heat-treatment/processing procedure that has the potential to increase high temperature strength has also been investigated. The method involves introducing work hardening through deformation and then performing a heat-treatment to stabilise deformation induced defect structure.