Simulations of fully three-dimensional model nanocrystalline face-centered cubic metal microstructures were used to study grain-boundary diffusion creep; which was considered to contribute to the deformation of nanocrystalline materials. To overcome the well-known limitations associated with the relatively short time interval used in molecular dynamics simulation (typically <10-8s), they were performed at elevated temperatures where the distinct effects of grain-boundary diffusion were clearly identifiable. In order to prevent grain growth and thus permit steady-state diffusion creep to be observed, the input microstructures were tailored to have a uniform grain shape and a uniform grain size of nm dimensions and to contain only high-energy grain boundaries which were known to exhibit rather fast liquid-like self-diffusion. The simulations revealed that, under relatively high tensile stresses, these microstructures indeed exhibited steady-state diffusion creep that was homogeneous, with a strain rate that agreed quantitatively with that given by the Coble-creep formula. The grain-size scaling of the Coble creep was found to decrease from d-3 to d-2 when the grain diameter became of the order of the grain-boundary width.

Grain-Boundary Diffusion Creep in Nanocrystalline Palladium by Molecular-Dynamics Simulation. Yamakov, V., Wolf, D., Phillpot, S.R., Gleiter, H.: Acta Materialia, 2002, 50[1], 61-73