In this work, a viscoplastic constitutive model for nanocrystalline metals was presented. The model was based upon competing grain boundary and grain interior deformation mechanisms. In particular, inelastic deformations caused by grain boundary diffusion, grain boundary sliding and dislocation activities were considered. Effects of pressure on the grain boundary diffusion and sliding mechanisms were taken into account. Furthermore, the influence of grain size distribution on macroscopic response was studied. The model was shown to capture the fundamental mechanical characteristics of nanocrystalline metals. These include grain size dependence of the strength, i.e., both the traditional and the inverse Hall–Petch effects, the tension–compression asymmetry and the enhanced rate sensitivity.

A Constitutive Model of Nanocrystalline Metals Based on Competing Grain Boundary and Grain Interior Deformation Mechanisms. E.Gürses, T.El Sayed: Materials Letters, 2011, 65[23-24], 3391-5