A heterogeneous structure by designing soft/hard domains with dramatically different strengths is effective to maintain the high ductility of metals but it sacrifices the yield strength. Here we first demonstrate a simultaneous enhancement of yield strength and tensile elongation by ∼20% in graphene nanosheet (GNS)/Al-Cu-Mg nano-laminated composites, with a tensile strength of ∼687 MPa and elongation over 10%, by designing heterogeneous domains with a little difference. The underlying mechanism was investigated by microstructural characterizations and simulations, and the hetero-deformation-induced hardening and nano-precipitation strengthening were mainly responsible for the strength-ductility synergy. This study broadens the understanding of heterostructured materials in pursuit of extraordinary mechanical properties. GRAPHICAL ABSTRACT IMPACT STATEMENT A novel heterogeneous nano-laminated structure with little domain difference was designed to achieve an excellent strength-ductility combination in GNS/Al-Cu-Mg composites.

Nanocrystalline (nc) metals typically possess high strength but low ductility. Here, we report an interface nanostructuring design via plasma assisted ball milling (PABM) to fabricate disordered multilayer graphene (DMGr)/Cu composites that are ultra-strong yet plastic, achieving a compressive strength of 1.56 GPa and plastic strain of exceeding 0.6. Our strategy relies on the uniformly and densely dispersed DMGr with sp²-sp³ hybridization. Interlayer sliding of DMGr but much stronger than van der Waals forces which can be anticipated to mediate plastic deformation and improve the plasticity. The high intrinsic strength of DMGr and associated Cu lattice strain near the interface due to strong interactions between DMGr and matrix can significantly impede dislocation motion and promote dislocation accumulation within nanograin interior. Ex-situ and in-situ TEM characterizations revealed that substantial dislocation interactions and accumulations induced by DMGr and the associated lattice strain along with interlayer sliding of DMGr, led to high strength, enhanced strain hardening capacity and superior plasticity. Such a design strategy provides a pathway for mitigating the trade-off between strength and plasticity in nanograined metals.