Grain refinement and its effect of polycrystalline metals during high strain rate deformation: Crystal plasticity modeling

Corresponding to the continuous dynamic recrystallization mechanism, we proposed a dislocation entanglement model and an energy-based criterion to capture the formation of subgrain boundaries during high strain rate deformation. A physical relationship between grain refinement and dislocation evolution is established and incorporated into the crystal plasticity constitutive model, where the spatial position of the subgrain boundaries can be determined by the energy minimization path. The developed constitutive model is implemented to simulate the dynamic compression and tension tests of pure copper by the crystal plasticity finite element method. Results show that the developed grain refinement model based on the dislocation entanglement gives good agreement with the experimental data validating its feasibility and rationality. The strengthening effect of grain refinement on the flow stress of metals at high strain rates depends on the competition between the strengthening of grain boundary and the softening of dislocation consumption during grain refinement. Further, a series of dynamic compressions are performed on copper samples with different grain sizes to explore the strengthening effect of grain refinement. The corresponding mechanisms of strengthening are analyzed and their respective contributions are also discussed in detail. The developed model can accurately predict the grain refinement of metals and capture its effect on strain hardening under high strain rate deformation.