Molecular dynamics investigation of plastic deformation mechanism in bulk nanotwinned copper with embedded cracks

•Plastic deformation of defective bulk nanotwinned copper has been explored.•Dislocation pile-up and transformation at twin boundaries are dominant.•Twin boundary dislocation pile-up zone is predicted to be 5.6–8 nm in width.•The flow stress vs. dislocation density follows the Taylor-type relationship.

The plastic deformation of bulk nanotwinned copper with embedded cracks under tension has been explored by using molecular dynamics simulations. Simulation results show that the cracks mainly act as dislocation sources during the plastic deformation and occasionally as sinks at later stage. The dislocation pile-up, accumulation and transformation at twin boundaries (TBs) control the plastic hardening and softening deformations. The TB dislocation pile-up zone is estimated to be 5.6–8 nm, which agrees well with previous experimental and simulation results. Furthermore, it is found that the flow stress vs. dislocation density at the hardening stage follows the Taylor-type relationship.