On elastic-viscoplastic modeling of nanotwinned metals based on coupled intra-twin and twin-boundary-mediated deformation mechanisms

An elastic-viscoplastic model has been developed for nanotwinned (nt) metals based on coupled intra-twin and twin-boundary-mediated (TBM) deformation mechanisms. The grain-size dependence of intra-twin plasticity was incorporated in the proposed model to determine the transitional twin thickness corresponding to the maximum strength. In addition, the joint distribution of grain size and twin thickness was also taken into account to simulate the microstructure of nt metals. The results obtained show that the TBM deformation mechanism dominated at low strain rate and small twin thickness, and that the grain-size and twin-thickness distributions had significant influence on the macroscopic behavior of nt metals. A linear relation between the transitional twin thickness and grain size is predicted by the proposed model, which is in good agreement with the results obtained from three-dimensional molecular dynamics simulations and experiments.