Work-hardening mechanisms in 2-phase γ-TiAl alloys were characterized, using transmission electron microscopy, in terms of the glide obstacles which governed the velocity and slip path of dislocations. It was found that there was clear evidence that short-range obstacles in the form of dislocation debris and dipoles were produced during room-temperature plastic deformation. These obstacles contributed significantly to the work hardening. An observed marked strain hardening arose from long-range elastic dislocation interactions, and the production of dipole and debris defects. Thermal stability of these deformation-induced defects was assessed by means of isothermal and isochronal annealing. The results indicated that the dipole and debris defects were relatively unstable to annealing at moderate temperatures; leading to appreciable recovery of the work hardening.

Work-Hardening and Recovery Mechanisms in Gamma-Based Titanium Aluminides. J.D.H.Paul, F.Appel: Metallurgical and Materials Transactions A, 2003, 34[10], 2103-11