Dislocation velocity and slip on the {‾12‾12} systems of zinc

Abstract

Slip bands on the {‾12‾12} systems of zinc were produced by stress pulses and were observed by etch pitting.. Edge and screw dislocation velocities as a function of stress and temperature (77° to 323°K) were deduced by measurement of the size of the slip bands. For the low temperature range of 77° to 110°K it is found that dislocation velocity is proportional to (stress) exp(-U/kT) where U = 0.182 ev. Screw dislocation velocity is found to be larger than edge dislocation velocity at a constant stress. It is suggested that a Peierls mechanism controls the dislocation velocity for the low temperature range. Above 110°K the slip bands start to become wider as cross glide takes precedence over the Peierls mechanism for the limitation of dislocation velocity. It is found that dislocation velocity decreases and the amount of cross glide increases with increasing temperature. It is suggested that the dislocations are retarded by an increasing number of dragging dipoles. The experimentally measured dislocation velocities are also related to the macroscopic measurements of the yield stress and the work hardening coefficient.