Diffusion of the 63Ni radiotracer in a well-compacted nanocrystalline (80 to 100nm) γ-phase 40wt%Ni alloy was measured by using serial sectioning at 610 to 1010K. The microstructure exhibited 2 different length-scales, with nano-sized grains that formed μm-sized clusters (or agglomerates). Three main diffusion paths governed the diffusion behavior: nanocrystalline grain interior,

nanocrystalline grain boundaries and inter-agglomerate interfaces. The absolute values, and Arrhenius parameters for Ni grain boundary diffusion,

D (m2/s) = 9.3 x 10-4 exp[-177(kJ/mol)/RT]

in the nano- γ-phase alloy were similar to those for Ni grain boundary diffusivity in coarse-grained polycrystalline γ-Fe. The inter-agglomerate interfaces, which represented the fastest diffusion path,

D (m2/s) = 1.9 x 10-3 exp[-134(kJ/mol)/RT]

were expected to be in a non-equilibrium state.

S.V.Divinski, F.Hisker, Y.S.Kang, J.S.Lee, C.Herzig: Interface Science, 2003, 11[1], 67-80