Study of low temperature plastic deformation mechanisms of alpha-titanium single crystals

The importance of the Peierls mechanism in the plastic deformation behavior of titanium is emphasized, as is the case of BCC metals. A non-planar core structure of screw dislocations was proposed; the core is dissociated simultaneously in one prismatic plane (10 bar 10) and two 1st order pyramidal planes (10 bar 11) and (10 bar 1 bar1). The model of the core structure permitted qualitative explanation of various experimental results associated with the movement of screw dislocations (macro yield stress) which needs a recombination of the partials lying out of the slip plane. The hardening effect of inertial impurities was explained by introducing a modification of the core structure by the presence of impurities in the form of clusters (chemical interaction). This modification makes the recombination of the core more difficult. The presence of stage II on the stress vs strain curve at 77 K was explained by the fact that the micro yield stress corresponding to the propagation of edge dislocations was relatively high. That seems to be a particularity of titanium, at least, within the purity range of the titanium used.