A NEW MODEL FOR THE PEAK OF ACTIVATION AREA OF ALPHA-TITANIUM

For prismatic slip in alpha titanium, the temperature dependence of th e activation area peaks at around 350 K in specimens of moderate purit y. TEM in situ deformation experiments have been performed between 150 and 473 K in order to determine the origin of this peak. In the entir e temperature range, rectilinear screw dislocations are found to move by jumps between locking positions. The jump length decreases as the t emperature is increased. This last experimental result is at the origi n of the present model. This jump length variation leads indeed to sev eral transitions between the microscopic mechanisms controlling the di slocation propagation. For each mechanism, the activation area is calc ulated as a function of stress. A global evolution of the activation a rea is obtained and compared with the data reported in the literature.