Tensile deformation properties of single crystal copper with nanotwins

The tensile properties along the 〈111〉 direction of single crystalline copper with 90° nanotwins are investigated by molecular dynamics simulation. The following results are observed. First, twin boundaries do not serve as a dislocation source at the very beginning of plastic deformation; instead, dislocations nucleate inside the crystal between the twin boundaries. Second, twin boundaries provide obstacles to the motion of dislocations on the inclined glide plane, and allow dislocations to move through at high stress. When the spacing of the twin boundaries is greater than 10 nm, deformation twinning starts to form during plastic deformation. Third, the flow strength of single crystal copper with nanotwins increases as the twin spacing decreases, which resembles a Hall-Petch like relationship. The strengthening mechanism is explained by a simple dislocation model.