Effects of Grain Size, Orientation, and Source Density on Dislocation Configurational Energy Density

The effects of grain size, source density, and misorientations on the dislocation configurational energy area density are investigated using two-dimensional discrete dislocation plasticity. Grain boundaries are modeled as impenetrable to dislocations. The considered grain size ranges from 0.4μm2 to 8.0μm2. The configurational energy area density displays a strong size dependence, similar to the stress response. Two sets of materials are considered, with low and high source/obstacle density. The high-source-density specimens exhibit negative configurational energy, implying that the dislocation structure is more stable than for isolated dislocations. The contribution of misorientation to the configurational energy density is analyzed using specimens with a single orientation or a checkerboard arrangement. The configurational energy density is found not only to depend on the dislocation spacing but also to be related to the local stress states. Low source densities lead to higher (positive) configurational energy densities.