Barrier parameters and statistics controlling the plasticity of Ti‒O solid solutions in the temperature range 20–550 K

Abstract

Detailed thermal activation analysis has been carried out on experimental data for the plasticity of polycrystalline titanium containing 0·06–1·6 at.% O in the temperature range 4·2–600 K. The analysis of the dislocation-impurity interaction parameters took into consideration the variations in the shear modulus and internal stress with temperature and the fact that the impurity distribution along dislocations can have various statistics. Values of the energy and maximum force of the dislocation-impurity interaction, the “depth” of the obstacle (the interaction region), the pre-exponential factor in the Arrhenius equation, as well as the average dislocation segment length and the internal stress, have been determined. It has been shown that in the range below 550 K the kinetics of plastic strain in Ti-O alloys are controlled by thermally activated motion of dislocations through barriers formed by oxygen atoms. The specific features of the change in the plasticity parameters of α-Ti usually observed at T _K > 300 K (as in the case of Zr and Hf) are due to the statistics of barrier distribution along a dislocation and not to alteration of the barrier type.