Mobile dislocations and internal stresses in the latent hardening of lithium fluoride crystals

Abstract

The density of mobile dislocations in gamma-irradiated LiF single crystals has been determined by measuring the potential difference developed between the side surfaces of a specimen while compressing it between tilted plates. It has been found that the density of mobile dislocations in the latent deformation is about half that in the primary deformation and the density in the soft deformation is about twice that in the latent deformation. Stress-relaxation tests have been performed on unirradiated as well as irradiated LiF single crystals during primary, latent and soft deformations. It is found that 90% of latent hardening is due to an increase in internal stresses and only 10% is due to an increase in effective stresses. Similarly, when the slip directions are reversed, softening is mainly due to the lower internal stresses.