A new microstructural model based on dislocation generation and consumption mechanisms through severe plastic deformation

A new model on the evolution of dislocation structure of cell forming metals and alloys through severe plastic deformation is presented. Following previous approaches, the model considers a cellular dislocation structure consisted of two phases: cell interiors and cell walls. The model distinguishes edge and screw dislocations in terms of three categories: mobile dislocations, immobile dislocations in cell interiors and immobile dislocations in cell walls. Then considering physical and geometrical assumptions for each dislocation category, an evolutional law is derived, based on some dislocation interaction mechanisms such as dislocation generation, annihilation, locking and migration. The model is applied on a severe plastic deformation process of aluminum called constrained groove pressing. The outputs of model are detailed description about dislocation densities (densities of edge and screw dislocations of all three mentioned categories) and cell size evolutions during deformation. To verify the results of modeling, X-ray diffraction patterns of deformed samples are analyzed. The achieved dislocation densities and cell sizes from the X-ray tests are compared with that achieved from the model and a good agreement is obtained.

Research highlights
► A new model on the evolution of dislocation structure of cell forming metals and alloys through severe plastic deformation is presented.
► The model distinguishes edge and screw dislocations in terms of three categories: mobile dislocations, immobile dislocations in the cell interiors and immobile dislocations in the cell walls.
► Considering physical and geometrical assumptions for each dislocation category, an evolution law is derived taking into account dislocation generation, annihilation, lock formation and migration mechanisms.