Orientation influence on grain size effects in ultrafine-grained magnesium

The mechanical behavior of ultrafine-grained magnesium was studied by discrete dislocation dynamics (DDD) simulations. Our results show basal slip yields a strong size effect, while prismatic and pyramidal slips produce a weak one. We developed a new size-strength model that considers dislocation transmission across grain boundaries. Good agreement between this model, current DDD simulations and previous experiments was observed. These results reveal that the grain size effect depends on three factors: Peierls stress, dislocation source strength and grain boundary strength.