Achieving Good Strength–Plasticity Compatibility in Cu Composites via Carbon Nanotube‐Induced Heterogeneous Bimodal Structure

Traditionally, metal matrix composites reinforced with uniformly dispersed carbon nanotube (CNT) have shown significant enhancement in strength, but always accompanied by the deterioration of uniform elongation (UE). Herein, a novel strategy is proposed to achieve the prominent strength–ductility combination of CNT‐reinforced Cu composites. The strategy makes use of the architecture design via mixing the CNT/Cu composite powders (prepared by the molecular‐level mixing method) with coarse‐grained Cu powders. The bulk composites with a controlled inhomogeneous microstructure are designed and fabricated, in which the reinforcing phase is inhomogeneously distributed at the microscale but homogeneous at the macroscale. The effects of fine and coarse grain proportions on the microstructure evolution and plastic deformation capacity of bimodal‐grained Cu composites are investigated. When the mixed ratio of refined CNT/Cu powder to coarse‐grained Cu is 1:1, the ultimate tensile strength (UTS) and UE of bimodal‐grained Cu composites are 384 MPa and 26.9%, respectively. Such good strength–plasticity compatibility is attributed to the combined effects of hetero‐deformation‐induced (HDI) stress and CNT strengthening mechanisms. This study provides insights for evading the strength–ductility trade‐off in high‐performance metal matrix composite by architecture design.