Reserch On Fabrication And Microstructure And Properties Of Graphene/Cpper Composites

Because of the excellent electrical and thermal conductivities,high ductility and toughness and admirable corrosion resistance of copper,copper and copper alloys play an importance role in the field of electric.However,its poor softening resistance and mechanical properties at high temperature make a large restrict to the application of the copper with a rapid development in some fields,like contact wires of highspeed rail and resistance welding electrode.This article focuses on the fabrication of a high-value-performance resistance welding electrode.Graphene,a two-dimensional material with ultra-high strength and interest conductivity,is regarded as an effective reinforcing phase to metal matrix composites.Now,more and more studies indicate that the addition of graphene lead a significant improvement to properties of metal matrix composites.As a reinforced phase,graphene is expected to be used to copper matrix composite to fabricate a material with ultra-high conductivity and thermal conductivity,excellent mechanical properties and higher softening resistance.In this paper,the preparation of graphene/copper matrix composite bar was studied,the effects of different process parameters on the microstructure and properties of graphene/copper matrix composite bar were studied,and the strengthening mechanism of graphene was explored.Multi-layer graphene(MLG)electrolytic copper powder were used.And the graphene/copper matrix composite powders were prepared by low energy ball milling process.The influence of graphene contents at the properties of composite bar was studied.Here list mainly results:(1)Graphene/copper matrix composite bar with a volume fraction of 1.0% had the highest electrical conductivity in three volume fractions we studied.The highest electrical conductivity come to 111.5%IACS and achieved to ultra-high electrical conductivity of copper matrix.(2)It was found that the quality of composite bars sintered at 1000? was better than others,which would not cause a large amount of agglomeration of graphene and the integrity of sintered composites was good.In addition,it also had a great electrical conductivity and mechanical properties.(3)With the decreased of the extrusion temperature,the conductivity and strength of graphene/copper composite bars increased.The graphene/copper composite bar extruded at room temperature with the highest yield strength and tensile strength were 221.4 MPa and 345.2 MPa.Comparing to pure copper bulk extruded at room temperature,the addition of graphene brings 146.8% and 44.7%improvement to copper matrix.(4)As for the graphene copper matrix composite bars prepared by hot extrusion,graphene mainly distributed in crystal.The main strengthening methods include fine crystal strengthening,dispersion strengthening and twinning plasticizing.For the graphene copper matrix composite bars extruded at room temperature,graphene almost exists at the grain boundary,and the main strengthening methods are deformation strengthening,fine crystal strengthening and load transfer strengthening.(5)The study on the influence of graphene on the high-temperature properties to copper matrix composites suggested that.It was found that graphene could effectively inhibit the growth of recrystallized grains and produce fine grain strengthening,and this mechanism could make a benefit on the high-temperature properties of copper matrix.However,when the temperature comes to 550?,the mechanical properties of the material were obviously reduced due to the recrystallization of the copper matrix,which mostly eliminated the improvement of mechanical properties by clearing work hardening effect.