A new model for the peak of activation area of α titanium

For prismatic slip in α titanium, the temperature dependence of the activation area peaks at around 350 K in specimens of moderate purity. TEM in situ deformation experiments have been performed between 150 and 473 K in order to determine the origin of this peak. In the entire temperature range, rectilinear screw dislocations are found to move by jumps between locking positions. The jump length decreases as the temperature is increased. This last experimental result isat the origin of the present model. This jump length variation leads indeed to several transitions between the microscopic mechanisms controlling the dislocation propagation. For each mechanism, the activation area is calculated as a function of stress. A global evolution of the activation area is obtained and compared with the data reported in the literature.