Effect of distribution of grain boundary diffusivity on plastic flow of austenitic steel II: The role of dislocation annihilation in grain boundaries in the plastic flow of polycrystalline materials

Abstract

Analysis of the effect of temperature and grain size on the hardening process of polycrystalline material has been carried out, assuming that grain boundaries (GB) are the most important dislocations sinks, that the kinetics of dislocation annihilation are controlled by the mobility of GB dislocations and hence by GB diffusion, and that the GB diffusivity is characterized by statistical distribution. To verify the equations derived, tensile tests have been performed within the wide range of temperatures on 0.12C22Cr17Ni austenitic steel subjected to different variants of thermal treatment. It has been found that the course of the changes of the strain-hardening coefficient depends, on the one hand, on the diffusional properties of GB in a given state of material, and on the other hand on grain size and the strain rate applied. The direction and extent of the changes are more adequately described when the distribution of GB diffusivity is taken into account instead of the mean value of GB diffusivity.