Mobility of Basal Dislocations in Zinc

This paper reports the results of an experimental study in which basal dislocation velocities were measured in zinc as a function of stress, temperature and dislocation orientation. The velocities were measured using the direct or Gilman-Johnston technique in which the individual dislocations themselves are observed. Tests were performed on 99.999% purity monocrystals. The applied resolved shear stress ranged from 0 to about 20 x 10^6 dynes/cm^2, the load durations were in the microsecond range, the test temperatures were 300, 223, 173 and 123 °K, and the measured velocities ranged from about 200 to 2000 cm/sec. Since the velocities are a linear function of stress and the velocity at a given stress increases with decreasing temperature, the velocity controlling mechanism is believed to be an interaction between the moving dislocations and the thermal waves of the lattice. The phonon viscosity and the phonon scattering mechanisms are compared to the data