Work hardening and recovery of gamma base titanium aluminides

Micromechanisms of deformation contributing to work hardening of gamma-base titanium aluminides at room temperature have been investigated. Deformation has been considered as stress driven thermally activated process and the experiments described were designed to identify the nature of glide obstacles generated during deformation. The investigations involve mechanical testing, electron microscope observations of the defect structure and recovery experiments. The investigations give supporting evidence 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 and can be overcome with the aid of thermal activation. These defects probably give rise to a significant recovery of the work hardening upon annealing. (C) 1999 Elsevier Science Ltd. All rights reserved.