Role of Peierls relief in low-temperature plasticity of α-solid solution Ti–Nb

The most commonly used Ti alloys are two-phase, consisting of the α- (hcp) and β- (bcc) allotropes of Ti. Varying the relative phase contents (considering the properties of each) allows the production of alloys with specified physical and mechanical properties. This paper examines the dislocation mechanisms that govern the plastic deformation rate of α-Ti–Nb solid solutions, which are characterized by unique functional properties such as high corrosion resistance, superconductivity, and biocompatibility. The temperature dependences of the yield strength and strain rate sensitivity of α-Ti–Nb alloys under quasi-static tension in the temperature range of 1.7–423 K are determined. The experimental results are discussed within the framework of a theoretical model of thermoactivated dislocation string motion in the Peierls relief. It is shown that the studied temperature range can be divided into three intervals, each with its own specific characteristics of dislocation motion in the Peierls relief. In the temperature range of approximately 18 to 150 K, the plastic deformation of α-Ti–Nb substitutional solid solutions is governed by the overcoming of Peierls stresses by dislocations through the nucleation, expansion, and annihilation of kink pairs—a mechanism characteristic of high-purity titanium. In the temperature range from 150 to 423 K, prismatic slip is controlled by another, as yet unidentified, thermally activated process. At temperatures below 18 K, plasticity is governed by a thermo-inertial mechanism associated with the transition, as temperature decreases, from thermally activated dislocation motion to dynamic (over-the-barrier) motion driven by the inertial properties of dislocations.