An Atomistic-to-Continuum Prediction of the Dislocation-Interface Reactions and the Subsequent Structure Changes in Metallic Composites under Deformation

When metallic composites are plastically deformed, the interaction between dislocations and the buried interfaces in them dictate their microstructure evolution and overall performance. In such interactions, a dislocation pileup usually forms and in turn, modifies the local stress state. In this scenario, the dislocation-interface reaction is multiscale in nature since both the atomic structure of the interfaces and the long-range stress field associated with the dislocation accumulation near the interface come into play. In this work, we expand our in-house concurrent atomistic-continuum (CAC) simulation tool for (i) measuring the local stress ahead of a long-range dislocation pileup; and (ii) determining its role in the subsequent structure changes, such as phase transformation (PT), shear banding, and cracking. The interfaces to be investigated include the phase boundaries (PBs) in multi-phase metallic composites, and the amorphous/crystalline interfaces (ACIs) in biomimetic multilayered amorphous/crystalline metallic composites (AC-MCs). The atomistic mechanisms responsible for the micrometer-level long-range stress-controlled structure changes induced by the dislocation-interface reactions are revealed. In details, in multi-phase metallic composites under a combined compression and shear, the dislocation-PB reaction is found to always follow a PT. The critical normal stress required for the PT nucleation can be largely reduced when a large number of dislocations are piled up at the PB. In a typical A/C-MC, CuZr/Cu, the absorption of dislocations at the ACIs lead to yielding of amorphous phases. This work will elucidate the discrepancies between atomistic simulations and experimental observations of dislocation-interface reactions, and highlight the importance of simulating such material behavior using concurrent multiscale methods.