Atomistic and phase field modeling of dislocation and solute interaction in alloysWednesday (06.11.2019) 11:45 - 12:05 Part of:
In many engineering alloys, defect evolution is strongly coupled to the chemical composition. Local fluctuations in chemical composition introduces heterogeneity in material properties that affect defect formation and evolution. On the other hand, the thermodynamics at the defects themselves differ from the bulk causing chemical partitioning between the two regions. Due to its energy-based formulation, the phase field (PF) approach combined with mechanical defect modelling is ideally suited to study this strong two-way coupling between chemistry and defect evolution. A large deformation formulation of mechanical equilibrium is coupled with PF modelling, considering elastic anisotropy, concentration dependent stiffness, solute residual distortion, as well as the concentration dependence of dislocation and stacking fault energies. A conservative Cahn–Hilliard model is employed to describe solute concentration, while the non-conservative Allen–Cahn model is employed for defect evolution. The defects considered here are dislocations, precipitates. The entire energy model is calibrated using atomistic and / or CALPHAD information (in the latter case, for solute mobility and chemical energy). This ensure for example accurate treatment of core size and dislocation transformation pathways. In particular, the resulting atomistic phase-field chemomechanical model is capable of predicting solute segregation to defect structures and solute-defect interaction. Example of this are studied in a range of model alloy systems and the results are shown to be comparable to the atom probe tomography experiments.