Abstract:The poor thermal stability of metallic copper limits its applications. This study fabricated graphene-encapsulated fine-grained copper composites via chemical vapor deposition (CVD) and investigated graphene growth on fine-grained copper (about 1 μm diameter). Results showed that pure copper's grain size increased from 2.03 μm (600 ℃) to 18.2 μm (1000 ℃), with hardness decreasing from 91.56HV to 27.64HV. Interestingly, graphene-encapsulated composites maintained stable grain size distribution (1.25~1.35 μm) and hardness distribution (83.96~100.63HV) across the different temperatures. These findings demonstrated that the graphene encapsulation on fine-grained copper significantly enhanced thermal stability by inhibiting copper atom diffusion. Furthermore, the drawn composite wires fabricated from the graphene-encapsulated copper composites by annealing at 1000 ℃ showed a 53.9% increase in hardness, a 12% improvement in tensile strength, a 29.8% higher elongation, and a 6.8% reduction in electrical resistivity compared with the counterpart produced from pure copper. This work provided new insights for fabricating copper-based composites with superior thermal stability.