Understanding the strain rate sensitivity of nanocrystalline copper using molecular dynamics simulations

•While deforming at ε̇⩾5.105s-1 NC copper are not able to relax on MD timescale.•The GB’s mechanisms are enhanced while reducing the strain rate.•The increase of the strain rate delays the onset of dislocation nucleation and propagation.•The contribution of twinning mechanism to plasticity increases with the strain rate.