Architecture dependent strengthening mechanisms in graphene/Al heterogeneous lamellar composites

An architecture-based model revealing the architecture-strengthening mechanism correlations of Graphene/aluminum (GR/Al) composites with heterogeneous lamellar (HL) architecture is proposed. The microstructural features such as matrix grain size, shape, and orientation in HL GR/Al composites are drivers for the dislocation storage and strain hardening ability. The proposed model allows to describe the role of the HL design factors affecting the microstructural architecture in GR/Al composite and the strengthening mechanisms of the material. The improved mechanical properties are linked to strain hardening ability, the high dislocation storage capability of the coarse grain bands (CGBs) as well as the generation of further geometrically necessary dislocations (GNDs) in the GR/Al interfaces. Moreover, the optimal-alignment of the structural elements and GRs not only causes a combined effect of isotropic and kinematic strain hardening but also leads to higher levels of back stress and back stress hardening, respectively. Actually, the significant effect of the interfacial dislocations including GNDs on the internal stresses especially back stress, which leads to the generation of extra strain hardening is underlined. In a word, the proposed model, which is based on the dislocation induced strengthening mechanisms, enables to guide the processing-microstructure design. • The interface-dislocation interactions are more important in heterogeneous lamellar-bimodal structures compared to lamellar-ultrafine grained structure materials. • More dislocation stored at the UFG/UFG interface, which indicates that the dislocation annihilation rates at the graphene‑aluminum interface might be lower than pure GBs (CG/CG interface). • The lamellar UFGs consists of interface and GBAZ zones, whereas CGs were composed of GI, GBAZ and GB zones. • It is the increase of internal stress both effective and back stresses that are responsible for the higher strain hardening rates throughout the plastic deformation of the graphene‑aluminum composites. • Our results offer a concrete strategy to design and fabricate high-strength graphene‑aluminum composites with excellent strength-ductility combinations. A modified strain hardening model is developed to considering the contribution of matrix grain size, shape, and orientation and graphene‑aluminum interface.