Grain boundary diffusion in severe plastically deformed metals: State of the art and unresolved issues
S. V. Divinski.
Diffusion Foundations, 5, 57-73, (2015)
An overview of current understanding of diffusion properties of grain boundaries in severely deformed materials is presented. The results are evaluated with respect to the types of severe plastic deformation, defects introduced by such processing, and processing parameters. An extended hierarchy of diffusion paths is shown to exist in ultra- ne grained materials, with relative diffusion rates being different by orders of magnitude. Properties of deformation-modified grain boundaries, such as width, diffusivity, diffusion mechanism and freevolume excess, are examined. A model of deformation-modified state of general high-angle grain boundaries is discussed with respect to the underlying concept of free volume accumulation. The relaxation stages of the deformation-modified state of grain boundaries are analyzed.