Dislocation-blocking enhancement mechanism in monolayer fullerene/copper composites

The emerging monolayer fullerene (M-C₆₀) offers exceptional multifunctional properties, yet its role in reinforcing copper via dislocation-blocking remains unclear. Using molecular dynamics nanoindentation simulations, we compare single-crystal Cu, graphene/Cu, and M-C₆₀/Cu in surface-coated and embedded configurations. Key findings demonstrate that M-C₆₀ coating enhances hardness by 24.2% via its sp²-sp³ hybrid structure leading to stair-rod/Hirth dislocation multiplication and carbon-chain formation, outperforming graphene's sp²-based mechanisms. Embedded M − C₆₀ absorbs and reflects mobile dislocations, reducing Hirth/Stair-rod dislocations by 54.1% and 16.7% and thereby improving ductility. Compared to graphene, M-C₆₀ exhibits a 26.3% higher interfacial bonding-site density and superior stress buffering, enabling more versatile tuning of strength–ductility tuning. Strain-rate studies reveal that M-C₆₀/Cu retains hardness by resisting brittle fracture and sustaining dislocation loop formation, unlike graphene coatings that fail catastrophically. Elevated-temperature tests show that M-C₆₀ coatings uniquely sustain or increase dislocation density due to strong Cu–C bonding and rough surface morphology, while graphene/Cu softens through dislocation annihilation and reduced twinning. In addition, the hardness-enhancement and dislocation-blocking mechanisms of M-C₆₀ are intrinsic to the material and are not attributable to the indenter characteristics. This work establishes a dislocation-blocking design framework for metal matrix composites, resolving the longstanding strength-ductility trade-off through rational 2D/metal interface engineering.