Atomistic phase field chemomechanical modeling of defect-solute interaction in metallic alloys

The interplay between chemistry and defects is important in determining the material behavior of many engineering alloys. Spatial fluctuations in chemical composition result in heterogeneous material properties affecting in particular defect formation and evolution. In addition, the difference between defect and bulk thermodynamics results in chemical partitioning between these. Given its energy basis, phase field (PF) modeling combined with mechanical defect modeling is ideally suited to study this strong two-way coupling between chemistry and defect evolution. In the current model, large-deformation-based mechanical equilibrium is coupled with PF modeling of defects and chemistry. In particular, the model accounts for elastic anisotropy, concentration dependent stiffness, solute residual distortion, and the concentration dependence of defect and stacking fault energies. In addition, Cahn-Hilliard modeling of solute concentration is coupled with Ginzburg-Landau modeling of defect evolution. Particular defects considered here include dislocations, precipitates, and low angle grain boundaries. The entire energy model is calibrated using atomistic and / or CALPHAD information (in the latter case, for solute mobility and chemical energy). This ensures for example accurate treatment of core size and dislocation transformation pathways. A number of example simulations and comparison with experimental results from atom probe tomography and transmission electron microscopy will be given.