Micromorphic crystal plasticity versus discrete dislocation dynamics analysis of multilayer pile-up hardening in a narrow channel

Abstract

Size effects in the mechanical behavior of multilayer pile-ups embedded in channel microstructures are investigated in terms of work-hardening, plastic slip and geometrically necessary dislocations (GND) distributions. The mechanical responses with various channel sizes are computed by three-dimensional discrete dislocation dynamics (DDD), micromorphic crystal plasticity (Microcurl) and field dislocation mechanics (FDM). The analysis is first limited to single slip with a slip plane perpendicular to the channel walls. In DDD simulations, it is found that the overall work-hardening is strongly dependent on distance between neighbor slip layers. The size dependence disappears when the neighbor layers are close enough to interact with each other. It is confirmed by direct comparison between DDD simulations and two analytical expressions derived from simplified model of multilayer pile-ups. Distributions of slip and GNDs are presented and analyzed for various channel sizes. The cases of inclined slip plane and of double slip systems in a channel are also considered and investigated. The two alternative crystal plasticity theories, Microcurl and FDM, are then found to reproduce the results of DDD. In particular, quantitative correspondence is found between the Microcurl and DDD results.