Dynamic manifestation of point defects on flow stress and the role of grain boundary as vacancy sinks

The early dislocation mechanics prediction of point-defect generation during deformation and its possible effect on the flow stress were examined using polycrystalline aluminum in which the grain boundaries were sealed and non-sealed with iron solutes. The up- and down-changes of the strain rate clearly demonstrate that vacancy mobility dramatically affects the dislocation-defect response as a function of temperature. The vacancy-pinning effect is detectable at 195 K and reaches a maximum at 246 K. At higher temperatures, thermally assisted unpinning is observed and the dynamic effects of supersaturated vacancies are still effective at 300 K. The up-change results can determine the effective single-obstacle dislocation–dislocation strain rate sensitivity and the associated activation distance.