High-temperature deformation of CsI single crystals in different environments

High-temperature compressive strain of CsI single crystals has been studied in a wide range of temperatures (290-773 K) and strain rates (2x10-3-10-5 c-1) in different environments: in vacuum, inert atmosphere (argon) and in the air. Higher hardening, higher level of internal stresses, shortening of the glide stage as compared to experiments in vacuum and inert atmosphere have been observed in case of deformation in the air, which is caused by penetration of impurities from air to the crystal during deformation. The environment effect on the state of local obstacles for dislocation movements has been estimated from temperature dependence of internal long-distance stresses. It is shown that the test environment influences the superplasticity of CsI single crystals: it is delayed in the air and is more vivid in vacuum and in argon. (author)