Overcoming strength-ductility trade-off in bimodal metal matrix composite with 3D graphene-strengthened hetero-interface

Strength-ductility synergy has long been a challenge in the development of advanced metallic materials. In this study, we fabricated a novel bimodal-structured nickel matrix composite , which features in-situ synthesized three-dimensional graphene networks (3DGN) strengthening the hetero-interfaces between coarse-grained and fine-grained zones (CGZ and FGZ). Compared to the bimodal matrix, this 3DGN-reinforced composite exhibits remarkable enhancements of 30 % in yield strength, 40 % in ultimate tensile strength , and 40 % in uniform elongation, respectively, representing the highest comprehensive performance among nickel matrix composites and pure nickel obtained through cold rolling, severe plastic deformation , and dynamic plastic deformation as reported in the previous literature. The superior strength-ductility combination originates from the incorporation of 3DGN, which enables multiple strengthening and toughening mechanisms. Specially, the strength and strain hardening capability have been enhanced through improved dislocation storage capacity, a stronger hetero-deformation induced (HDI) hardening effect, and the activation of numerous stacking fault ribbons. Moreover, high-density dispersed microcracks in the FGZ relieve strain/stress concentrations while being constrained within the CGZ, further enhancing tensile ductility. This study provides new insights into addressing the inherent strength-ductility paradox in metal matrix composites . • A novel bimodal-structured nickel matrix composite with 3D graphene networks was fabricated. • 3D graphene networks strengthen hetero-interfaces, enhancing strength-ductility synergy. • 3DGN-reinforced composite shows 30 % increase in yield strength, 40 % in tensile strength, and 40 % in uniform elongation. • Enhanced strain hardening through improved dislocation storage, HDI hardening, and stacking fault activation. • Dispersed microcracks in fine-grained zones relieve stress without compromising ductility.