Preparation And Properties Of Modified Graphene Reinforced Copper Matrix Bulk Composites

Pure copper is widely used in industrial fields such as machinery,transportation and electronics because of excellent thermal conductivity,electrical conductivity and chemical stability.However,the application and development of pure copper are greatly limited due to low strength,low hardness and poor wear resistance.It is an effective method to improve comprehensive performance by introducing a reinforcing phase to the copper matrix and compounding the two to prepare copper matrix composites.Graphene is an ideal reinforcing phase for copper matrix composites owing to excellent structure and properties.It has become urgent problems to be solved in the preparation of high-performance copper matrix composites,which is due to easy agglomeration,poor dispersion and weak interfacial bonding of graphene in the copper matrix.Therefore,from the perspective of graphene modification,graphene oxide（GO）with good hydrophilicity is selected as the carrier in paper.The graphene-loaded copper（Cu@r GO）,nickel（Ni@r GO）and copper-nickel（Cu-Ni@r GO）composite powders were prepared by chemical reduction of the modified graphene,which were used for reinforced phase.Then,graphene-loaded copper,nickel and copper-nickel reinforced Cu matrix（Cu@r GO/Cu,Ni@r GO/Cu and Cu-Ni@r GO/Cu）bulk composites were prepared by ultrasonic powder mixing and spark plasma sintering.The influence of different loaded metals on the dispersion of graphene were studied.The effect of different reinforcements on the microstructure,structure,mechanical and electrical properties of bulk composites were analyzed,and the strengthening mechanism of bulk composites were explored.The main results are as follows:（1）In this study,using a certain quality of Cu₂₀₀@r GO,Ni₁₀₀@r GO and Cu₁₀₀-Ni₁₀₀@r GO composite powders were prepared by using GO,Cu（NO₃）₂·3H₂O and Ni（NO₃）₂·6H₂O as raw materials and hydrazine hydrate as reducing agent.The reduced Cu,Ni and Cu-Ni nanoparticles were evenly distributed in the interlayer and surface of graphene.The agglomeration of graphene was hindered and composite powders with good dispersion of graphene were obtained.（2）The microstructure,structure and properties of Cu@r GO/Cu,Ni@r GO/Cu and Cu-Ni@r GO/Cu bulk composites were analyzed.It is observed that the three reinforcing phases can be uniformly distributed in the copper matrix when the content is less than 2 wt.%.It can inhibit the growth of copper particles during the sintering process,so that the grain size of the copper matrix is significantly reduced,and the reinforcing phase is closely combined with the interface of copper matrix.The hardness and tensile strength of the bulk composites with the increasing of the reinforced phase content showed a trend of increasing and decreasing,and the density and electrical conductivity showed a trend of decreasing.（3）The microstructure,structure and performance comparison and strengthening mechanism of the modified graphene-reinforced copper matrix bulk composites were analyzed.The comprehensive performance of the bulk composite was better when the content of Cu@r GO was 1.5 wt.%,Ni@r GO was 0.5 wt.%,and Cu-Ni@r GO was 1 wt.%.The tensile strength was254 MPa,330 MPa and 254 MPa,respectively.The hardness was 88 HV,94 HV and 94 HV,and the density were 98.8%,91.9%and 96.3%,respectively.The electrical conductivity was86.7%IACS,87.8%IACS and 85.2%IACS,respectively.The elongations were 18%,21%and22%,respectively.The fracture mechanism presents ductile fracture by the fracture morphology analysis.Thermal mismatch strengthening of bulk composites was dominated,and fine grain strengthening and load transfer strengthening of bulk composites were supplemented.