Dislocation density-based crystal plasticity model for phase-field simulation
During the thermal and mechanical treatment of materials, martensitic phase transformations will cause internal stresses in metallic microstructures due to the volumetric and shape change of the crystal lattice. However, increasing stresses are limited by the onset of plasticity, which is the the motion of dislocations in the corresponding phase. From an energetic point of view, this plasticity-induced limitation or reduction of the elastic free energy is expected to shift the ratio towards further energy contributions like interface and chemical energy. Consequently the driving forces of the phase transformations and the final microstructure is expected to vary. The wish to understand these processes creates a demand of tools to couple (dislocation density-based) crystal plasticity models and the phase field method.
In the preceding project stage, a crystal plasticity model for FCC metals in the "OpenPhase" code - using a concept to treat local plastic strains and dislocation densities in the diffuse interface - has been implemented. A formulation of the energy of the dislocations enters the phase field model and will lead to a driving force tending to reduce grains with severe defects. In the current step, the elaborated model is going to be validated and applied to the analysis of stress induced grain boundary motion. Here, a special emphasis is put on the phase boundary - dislocation interaction modeling as well as the influence of local hardening due to statistically stored and geometrically necessary dislocations. Based on these results martensitic phase transformations simulations will be set up.