The solute diffusion of Ag in nanocrystalline γ-phase 40wt%Ni alloy was studied by using radiotracer techniques at 489 to 1200K. Powder metallurgy was used to produce nanomaterial which consisted of μm-sized agglomerates of nm-sized grains. Two types of internal interface acted as short-circuit paths for diffusion: nanocrystalline grain boundaries and inter-agglomerate interfaces. By combining recent results on Ag grain boundary diffusion in coarse-grained γ-Fe–40wt%Ni alloy, with the present diffusion data on nanocrystalline alloy, Ag segregation was determined as a function of temperature. The Ag segregated strongly at grain boundaries, with a segregation enthalpy of 47kJ/mol. Knowing the segregation factor, experimental data on Ag diffusion along nanocrystalline and inter-agglomerate interfaces in the nanomaterial were systematically analyzed. The sensitive radiotracer experiments, and subsequent diffusion profile analysis, resulted in a consistent set of diffusion data over the whole of the investigated temperature range. The Arrhenius behavior of Ag nano-grain boundary diffusion was described by:

D (m2/s) = 4.7 x 10-4exp[-173(kJ/mol)/RT]

while the much faster inter-agglomerate interface diffusion was described by:

D (m2/s) = 8.1 x 10-5exp[-91(kJ/mol)/RT]

S.V.Divinski, F.Hisker, Y.S.Kang, J.S.Lee, C.Herzig: Acta Materialia, 2004, 52[3], 631-45