The role of Peierls relief in the low-temperature plasticity of pure α-Ti

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A detailed investigation of the low-temperature plasticity of high-purity polycrystalline α-Ti (interstitial impurities O+N=0.06 at. %) is carried out. The temperature dependences of the yield strength, effective stress, rate sensitivity of the deforming stress, and activation volume are obtained in the temperature interval 0.5–450 K. A thermal-activation analysis of the experimental data is carried out in terms of a model of activated motion of a dislocation string in Peierls relief. It is shown that the plastic flow of pure α-Ti in the region of moderately low temperatures (7 K<T<150 K) results from thermally activated overcoming of Peierls barriers by the mechanism of generation, expansion, and annihilation of paired kinks. Empirical values are obtained for the parameters of the theory for {101¯0}〈112¯0〉 prismatic slip in α-Ti at low temperatures: the Peierls stress τP=72 MPa and the characteristic energy of a critical paired kink, Hc=1.5×10−19 J=0.96 eV. At T<7 K, the plasticity of pure α-Ti has a pronounced anomaly, which may be caused by a transition as the temperature is reduced, from a thermally activated regime of dislocation motion to a dynamic (over-barrier) regime. At elevated temperatures (T>150 K), the plasticity of pure α-Ti qualitatively maintains characteristic features that correspond to the mechanism of thermally activated dislocation motion in the Peierls relief for low values of the effective stresses.