Mesoscale modeling of mixed-type dislocations in face-centered cubic metals

Mixed-type dislocations are prevalent in face-centered cubic metals and play an important role in plastic deformation. Their key characteristics, such as the core structure and core energy, cannot simply be extrapolated from those of dislocations with 0^o and 90^o (screw/edge) character angles. Most studies, however, have been devoted to those of pure edge/screw type. In this work, we explore the core structure/energy/stress of mixed-type dislocations in Al using a variety of meso-scale dislocation models, i.e., phase-field dislocation dynamics, atomistic phase-field microelasticity, and concurrent atomistic-continuum modeling. The generalized stacking fault energy surface for Al is calculated using density functional theory and employed in the phase field modeling. Two atomic-level stress formulations are employed and compared. The issues of core energy double counting in phase field methods and grid/mesh sensitivity are explored. We then benchmark results against molecular statics and discuss possible sources of errors in these continuum calculations. A dislocation loop is then modelled using these approaches to shed light on their abilities to describe more realistic mixed-type configurations, potentially assisting in designing stronger metallic materials.