Mobile and immobile dislocations in LiF crystals under straining

Abstract

Immobile dislocations are observed by the method of selective etching in the course of crystal deformation of lithium fluoride crystals with the yield stress values 70 and 200 p/mm2. The method is described in the paper. The density of mobile dislocations in glide bands is obtained as the difference between the total dislocation density ϱ and that of immobile dislocations. The total density of dislocations is detected by a repeated etching of the crystal in the unloaded state. Mean values ϱi and ϱ of the immobile and mobile dislocation densities ϱ and ϱb, respectively, are established taking into account the active glide volume Va which is assumed to be equal to the volume of the glide layers involved in the deformation. An increase of ϱ and ϱi with the growth of the plastic strain e has been observed. The data obtained are compared with the information supplied by indirect experiments, and a qualitative agreement is established. [Russian Text Ignored.]