A full-field non-local crystal plasticity investigation of bi-layered HEA

Abstract

Heterogeneous deformation has been widely proven to provide extra strengthening in heterostructured metallic materials. However, the explicit modelling of underlying plasticity mechanisms at both grain and sample levels remains a challenge for the scientific community. For this reason, the research presented here reports on the development and testing of a novel non-local crystal plasticity finite element model to simulate the deformation of heterostructured metallic materials. This model explicitly includes geometrically necessary dislocations (GNDs), back stress hardening, a damage criterion and does not rely on a homogenisation scheme. This approach enables the numerical investigation of dislocation-mediated plasticity simultaneously at both grain and sample levels. The model was validated against experimental data when simulating the deformation of a bi-layered high entropy alloy (HEA). The obtained results aligned well with experimental findings. In particular, the simulations confirmed that shear bands (SBs) preferably propagate along grains sharing similar orientation while causing severe grain rotation. In addition, for the pair of grain sizes considered here for the bi-layered HEA i.e., 14 μm and 46 μm for the finer and coarser layers, respectively, GNDs did not tend to pile up at the interface between these layers but at the grain boundaries instead. It is suggested that this study provides a solid theoretical framework for the future design of heterostructured metallic materials to achieve optimal strength-ductility balance and to predict potential crack nucleation sites and SB evolution in such materials.