High-density nanocrystalline Au was prepared by using the gas deposition method. Various anelastic and plastic creep processes associated with the grain boundary regions were observed. Vibrating-reed measurements at 100Hz, and a strain amplitude of 10-6, revealed a very broad internal friction peak near to 95K, Qp,95 K-1, and a steep increase in anelastic strain above 200K, εa-I,>200 K. Tensile tests revealed a steep increase in the anelastic strain above 200K, εa-II,>200 K, for stresses above a few MPa and a linear plastic creep strain above 200K, εpc-1, for stresses ranging from 30 to 150MPa. Activation parameters, 1/τ0, of 3 x 1011/s and E of 0.16eV, were found for Qp,95 K-1, where τ0 and E were a pre-exponential factor and an activation energy for the relaxation time, τ. It was suggested that simple relaxation processes were responsible for Qp,95 K-1. The values of 1/τ0 and E which were found for εa-I,>200 K and εa-II,>200 K decreased with increasing applied stress or temperature; thus indicating that their atomic processes were the same. Furthermore, the E-value found for εpc-1 was similar to, or slightly smaller than, that for εa-II,>200 K. The observations indicated that the atomic motions in the grain boundary regions of nanocrystalline Au developed in scale in the order of the underlying processes for εa-I,>200 K, εa-II,>200 K and εpc-1, and were thus different from those for conventional polycrystalline Au.

Anelasticity Study on Motions of Atoms in the Grain Boundary Regions in Nanocrystalline Gold. H.Tanimoto, S.Sakai, H.Mizubayashi: Materials Transactions, 2003, 44[1], 53-8