Dislocation Velocity on the {1212}〈1213〉Slip System of Zinc

Abstract

Dislocation velocity on the {1212}〈1213〉slip systems of zinc monocrystals was deduced from the rate of growth of slip bands. Near 77°K dislocation velocity is directly proportional to stress, and screw dislocations move more rapidly than edge dislocations. The pre-exponential factor in a thermal activation model is the same for edge and screw dislocations, but the activation energy for edge dislocations (0.22eV) exceeds that for screws by 5%. It is postulated that the larger activation energy for edge dislocations is due to their dissociation in the basal plane. Near room temperature dislocation velocity decreases and cross-glide increases with increasing temperature. It is suggested that dragging dipoles are responsible for the decrease in dislocation velocity. Finally, it is shown that the temperature dependence of both the yield strength and the plastic modulus is similar to the temperature dependence of the stress required to produce a constant dislocation velocity.

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