Molecular dynamics study of bimodal nanotwinned Cu with a composite structure

Recently, a novel material with duplex microstructure has drawn continuous researching attention of material scientists, consisting of ultrafine grains as the matrix and coarse nanotwinned grains as the inclusions. Due to the twin boundaries (TB) strengthening effect, the coarse nanotwinned grains impart high strength. In our molecular dynamics simulation (MD), bimodal nanotwinned Cu model was established by means of embedding the coarse nanotwinned grain into the ultrafine grained matrix. Through the uniaxial tensile simulations, it is found that the flow stresses of bimodal nanotwinned Cu are related with the coarse nanotwinned grain size (d_c), twin boundaries spacings (TBSs) as well as twin orientation. The deformation mechanisms (e.g. TB migration, deformation twinning as well as TB-dislocations reactions) are explored in detail. The paper provides a first investigation on the novel material by MD analysis.