Thermally activated deformation mechanisms in micro-alloyed two-phase titanium amminide alloys

The processes controlling the dislocation mobility in micro-alloyed two-phase γ-titanium aluminides have been investigated over a wide temperature range by determining activation parameters of plastic deformation and TEM observations. The deformation behavior of the materials is characterized by a relatively high athermal stress component due to dislocation interactions with grain boundaries and lamellar interfaces. The glide resistance of the dislocations is controlled by several processes. At room temperature, the mobility of ordinary dislocations is determined by a combination of localized pinning and lattice friction. Additional glide resistance arises from nonconservative processes at jogs in screw dislocations and leads to a thermal contribution to work hardening. Dislocation climb processes start above 900 K and seem to initiate the transition from brittle to ductile material behavior.