The influence of grain size and temperature on the mechanical deformation of nanocrystalline materials: Molecular dynamics simulation

Nanocrystalline (nc) materials are characterized by a typical grain size of 1-100nm. The uniaxial tensile deformation of computer-generated nc samples , with several average grain sizes ranging from 5.38 to 1.79nm, is simulate d by using molecular dynamics with the Finnis-Sinclair potential. The influ ence of grain size and temperature on the mechanical deformation is studied in this paper. The simulated nc samples show a reverse Hall-Petch effect. Grain boundary sliding and motion, as well as grain rotation are mainly res ponsible for the plastic deformation. At low temperatures, partial dislocat ion activities play a minor role during the deformation. This role begins t o occur at the strain of 5%, and is progressively remarkable with increasin g average grain size. However, at elevated temperatures no dislocation acti vity is detected, and the diffusion of grain boundaries may come into play.