Cooperative-competitive effects of He bubbles and dislocation loops on plasticity and damage evolution in dynamically stretched single-crystal Cu

He bubbles and dislocation loops are two typical irradiation defects that significantly influence the dynamic tensile behavior of irradiated materials. In this work, the cooperative-competitive influence mechanisms of these two defects on dynamic tensile plasticity and damage evolution are investigated using molecular dynamics simulations. The results reveal that dislocation loops and He bubbles influence the plasticity of materials through different mechanisms: dislocation loops affect plasticity via dislocation dissociation and slip, whereas He bubbles through the surface dislocation emission induced by stress concentration. Dislocation loops dominate the initial plastic behavior, while He bubbles accelerate the later-stage plastic development. Regarding void nucleation, these two defects exhibit a competitive mechanism: dislocation loops promote void nucleation, while He bubbles suppress it. He bubbles play a more dominant role than dislocation loops in controlling the damage process of samples containing both defects. Additionally, the sensitivity of these defect-dominated mechanisms to strain rate (10⁸-10¹¹ s⁻¹) and defect density (0.5-8.6 × 10²³ m⁻³) is also systematically examined. These findings provide valuable insights into the defect-mediated tensile response specific to different deformation stages, offering mechanistic support for performance prediction and theoretical model construction of irradiated materials under extreme conditions.