Massively parallel molecular dynamics simulations of polycrystal plasticity were used to elucidate the intricate dislocation dynamics that evolved during the process of deformation of columnar nanocrystalline Al microstructures of grain size between 30 and 100nm. The mechanisms of dislocation–dislocation and dislocation–twin boundary reactions that took place under sufficiently high stresses were analyzed in detail. These reactions were shown to lead to the formation of complex twin networks, i.e. structures of coherent twin boundaries connected by stair-rod dislocations. Consistent with recent experimental observations, these twin networks may cause dislocation pile-ups and thus give rise to strain hardening.

Dislocation–Dislocation and Dislocation–Twin Reactions in Nanocrystalline Al by Molecular Dynamics Simulation. V.Yamakov, D.Wolf, S.R.Phillpot, H.Gleiter: Acta Materialia, 2003, 51[14], 4135-47