Simultaneous enhancement of strength and ductility in AlCu alloy via trans-granular graphene nano-shells

Strain localization at grain boundaries (GBs) is one of the key factors contributing to the trade-off between strength and ductility in engineering alloys. To address this issue, we developed a unique perpendicular interlocking structure connecting the matrix GBs by introducing trans -granular graphene nano-shells (SGSs) via a two-step targeted localized Cu–Al interdiffusion process. In the as-built structure, the original GBs served as the soft component, while the perpendicularly intersecting SGSs acted as the hard component. This configuration not only promotes sustainable dislocation accumulation in the vicinity of the GBs but also facilitates plastic strain delocalization through stress shielding effects from the SGSs. By effectively impeding the extension of shear bands and redirecting crack propagation towards the grain interiors, these hetero-structured GBs contribute to reducing the intrinsic brittleness of GBs. Consequently, the SGS/AlCu composite demonstrates a remarkable balance of tensile strength (∼574 MPa) and ductility (∼17 %). Our findings suggest that restructuring the geometry of GBs in metallic alloys presents a promising strategy for mitigating strain localization at GBs, offering potential for enhancing the properties of metallic alloys in various engineering applications.