High strength and plasticity in disordered multilayer graphene reinforced copper 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.