Basal dislocation mobility in zinc single crystals
Experimental measurements of basal dislocation mobility and the strain-rate sensitivity of the flow stress have been made on 99.999% pure zinc single crystals. Dislocation mobility in the  (0001) basal slip system was measured by observing slip band growth produced by load pulses of controlled amplitude and duration. Local rearrangement of dislocations occurs at a resolved stress of 7 lb./in.^2. Slip bands are formed at stresses greater than 7 lb./in.^2, and their growth velocities are in the range of 7 to 80 cm/sec for shear stresses between 7 and 12 lb./in.^2. The results of the experimental measurements of dislocation mobility are discussed in relation to current theories. A comparison of the strain-rate sensitivity and the mobility measurements shows that a significant change in the density of moving dislocations is associated with a change in strain-rate. This change in density has generally been ignored by previous investigators. A dislocation model is proposed to explain the observed strain-rate sensitivity.
Additional Information© 1967 Elsevier Publishing Company. Received November 14, 1966; revised March 6, 1967. The authors wish to express their appreciation to the U.S. Atomic Energy Commission for sponsorship of this work under Contract No. AT (04-3)-473. The invaluable assistance of A. P. L. Turner and R. C. Blish in specimen preparation, testing and data analysis is gratefully acknowledged.