Representation of a microstructure with bimodal grain size distribution through crystal plasticity and cohesive interface modeling

The microscale loading effects in a bimodal Al 5083 microstructure are examined through finite element modeling. A crystal plasticity model is adapted to this problem and its parameters are derived from the material properties of pure Al through representation as the additive combination of effects attributable to grain size and solute strengthening. This model is used in conjunction with a cohesive interface grain boundary description. Large scale and microscale finite element models are procedurally generated and used in a multiscale model fitting process to extract the necessary properties of conventional (coarse grained) and ultrafine grained Al 5083. The results of these simulations show large strain concentrations between closely spaced coarse grains, highlighting the activity of these areas in the final failure behavior of the material. At the microstructural level, individual grains oriented in more compliant configurations are observed to experience high strains, which place stresses on adjacent grains. These results suggest a competition between inter- and intragranular fracture mechanisms.