Dislocation–dislocation and dislocation–twin reactions in nanocrystalline Al by molecular dynamics simulation

We use massively parallel molecular dynamics simulations of polycrystal plasticity to elucidate the intricate dislocation dynamics that evolves during the process of deformation of columnar nanocrystalline Al microstructures of grain size between 30 and 100 nm. We analyze in detail the mechanisms of dislocation-dislocation and dislocation-twin boundary reactions that take place under sufficiently high stress. These reactions are 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.