Grain boundary diffusion characteristics of nanostructured nickel

Using copper grain boundary diffusion in nickel as an example it has been shown that the grain boundary diffusivities in nanostructured metals processed by means of severe plastic deformation (SPD) in the temperature range of 398-448K are 4-5 orders of magnitude higher relative to the same materials in a coarse-grained state. The experimentally measured activation energy of grain boundary diffusion is close to that of free surface diffusion despite the absence of residual porosity in the investigated materials. The increase of diffusion permeability of interfaces observed for SPD Ni relative to coarse-grained and nanostructured electrodeposited Ni is attributed to a special non-equilibrium (high-energy) state of the grain boundaries in the metals processed by means of severe plastic deformation.