Dislocation Mobility in the {1122} 〈1123〉 Slip System of Zinc Single Crystals

Abstract Results are presented of measurements of the stress dependence of screw dislocation velocities in the {11 2 2} 〈11 2 3〉 slip system (pyramidal slip) of zinc single crystals. The investigations have been carried out on zinc single crystals of 99.999% purity at room temperature. The dislocation mobility has been studied within a wide range of velocities and shear stresses below and above the critical resolved shear stress. When the shear stress τ changed from 20 to 4000 p/mm 2 the dislocation velocity v varied from 10 −3 to 10 4 cm/s. A strong dependence of v on τ is observed in the stress range 20 to 100 p/mm 2 , which can be described by an exponential and the dislocation mobility is determined by a thermally activated mechanism. A weak linear dependence of v on τ is observed at shear stresses greatly exceeding the critical shear stress (300 to 4000 p/mm 2 ). These results are explained in terms of a phonon viscosity mechanism. The measured drag constant is of the same order of magnitude as that calculated for the mechanism of phonon viscosity.

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