The deformation behavior of polycrystalline Cu nanowires under tension, bending and torsion was first studied by using molecular dynamics simulations. The results show that both free surfaces and grain boundaries could control the plastic deformation. In detail, for polycrystalline Cu nanowires under tension, the stress-assisted grain growth caused by atomic diffusion and grain boundary migration was found, which was thought to be the reason for necking. Then under the bending effect, full dislocations and deformation twins of polycrystalline Cu nanowires were found in the grains. Moreover, the twin boundaries act as obstacles to dislocation motion. Finally, full dislocations and fivefold deformation twins were detected in polycrystalline Cu nanowires in the torsional state. These phenomena were in good agreement with the experimental observations of Liao et al (2005). The second part investigates the effects of sample shape and crystallographic structure on the modulus and yield strength under tension, bending and torsion. The results demonstrate that the modulus (in particular the bending and torsion modulus) could be significantly influenced by both the effects; however, remarkable difference in yield strength could merely be caused by different crystallographic structures (here, different crystallographic structures refer to polycrystalline and single-crystalline structures).

Investigations on the Deformation Behavior of Polycrystalline Cu Nanowires and some Factors Affecting the Modulus and Yield Strength. X.Tian, J.Cui, B.Li, M.Xiang: Modelling and Simulation in Materials Science and Engineering, 2010, 18[5], 055011