Molecular Dynamics Simulation on Plastic Deformation of Nanocrystalline Copper

摘要

Molecular dynamics (MD) simulation is used to simulate the plastic deformation of a nanocrystalline model Cu sample with an average grain size of 5 nm containing 27 grains under high strain rate shear loading. Results show that the plastic deformation of nanocrystalline copper can be divided into two parts: grain sliding dominated part, dislocation motion and grain sliding together dominated part. When the shear strain is less than 4%, the macro plastic deformation is the result of relative sliding of grains, grain rotation does not contribute to the overall plasticity, but it plays a supporting role in grain network adjustment. In this part, the deformation process can be described by viscous flow model. When the strain is greater than 4%, a large number of partial dislocations nucleate in grain boundaries and then slip into grains, most of them finally annihilate in corresponding grain boundaries and some deformation twins emerge near triple junctions. Therefore, the plastic deformation is the result of grain sliding, dislocation slipping and twinning. During shear deformation, shear planes involving several grain boundaries which are sub parallel to the loading plane have been observed.