Interface effect on dislocation structure of deformed radiation-hardened layered LiF crystals

Interface effect on the evolution of dislocation structure accompanying plastic deformation of layered LiF crystals under single-slip condition has been experimentally studied. The samples were prepared with X-ray irradiation of layers of LiF single crystals, interfaces between the irradiated ("hard") and unirradiated ("soft") regions being located along the specimen axis. It was found that plastic deformation under compression occurs by means of nucleation and development of slip bands in "soft" regions followed by their penetration into "hard" regions. When screw dislocations intersected the interface their density in the irradiated region increased sharply (up to by a factor of three). In edge slip bands, the dislocation etch pit densities were approximately the same in different regions. Influence of the irradiation time and of irradiated region size on the yield stress has been studied, too. The obtained results can be explained by a difference in parameters of double cross slip and multiplication of dislocations before and after intersecting the interface.