| Owing to Graphene Nanoplatelet(GNP)has ultra-high strength and excellent thermal conductivity,electrical conductivity and other characteristics,so GNP is used to compound with Copper(Cu)and its alloys to prepare Copper Matrix Composites(CMCs).CMCs can not only maintain the electrical conductivity of Cu matrix,but also realize the synergistic strengthening effect of GNP and Cu9 so that CMCs can meet the performance requirements of high-strength and high-conductivity materials in electronic industry.However,how to promote the dispersion of GNP and improve the wettability between GNP and Cu is the main problem faced in current research.Therefore,this paper considers both composition design and preparation process.Firstly,it is proposed to improve the poor wettability between GNP and Cu by adding Nickel(Ni),Secondly,"Wet Mixing" process is used to improve the dispersibility of GNP,Spark Plasma Sintering(SPS)and Hot Extrusion method are used to prepare GNP-Ni/Cu composite with excellent performance.By characterizing phase composition and microstructure of material,and testing density,electrical conductivity and mechanical properties of material,on the one hand,this paper studies the influence of powdering process parameters on GNP dispersion,on the other hand,this paper studies the influence of GNP content and Ni content on the structure and properties of GNP/Cu composite.The results show that when the addition amount of ethyl alcohol absolute is 20 wt.%,powder mixing rate is 200 rpm,and powder mixing time is 3 h,the Van Der Waals force between ethyl alcohol absolute and GNP is greater than the Van Der Waals force between GNP flakes.At the same time,the mechanical shearing force of grinding ball further destroys the Van Der Waals force between GNP flakes,so GNP dispersion effect is good and it is evenly distributed on the surface of flake Cu powder.When GNP content is 0.2 wt.%,the microhardness,yield strength and electrical conductivity of GNP/Cu composite are 86 HV,199 MPa and 93.38%IACS,respectively.Compared with pure Cu,the microhardness and yield strength of GNP/Cu composite are increased by 21%and 34%,respectively,while the electrical conductivity of GNP/Cu composite is only reduced by 3.0%.In order to improve the wettability between GNP and Cu,Ni is added to improve the interface bonding between GNP and Cu.When the content of GNP and Ni are 0.2 wt.%and 1.5 wt.%,respectively,the overall performance of GNP-Ni/Cu composite is optimal.The microhardness,yield strength and electrical conductivity of GNP-Ni/Cu composite are 98 HV,222 MPa and 42.54%IACS,respectively.Compared with pure Cu,the microhardness and yield strength of GNP-Ni/Cu composite are increased by 38%and 50%,respectively,while the electrical conductivity of GNP-Ni/Cu composite is reduced by 55.8%.Compared with 0.2GNP/Cu composite,the microhardness and yield strength of GNP-Ni/Cu composite are increased by 14.0%and 11.6%,respectively,and the electrical conductivity of GNP-Ni/Cu composite is reduced by 54.4%.The above results show that the addition of Ni can not only effectively improve the interface bonding between GNP and Cu,but also significantly improve the mechanical properties of GNP-Ni/Cu composite,but the material's electrical conductivity loss is greater.In order to clarify the strengthening mechanism of composite.The microstructure of the sample was analyzed by SEM,TEM,EBSD and other analytical methods,and it was found that the improvement of mechanical properties of GNP-Ni/Cu composite was the combined effect of load transfer strengthening,thermal mismatch strengthening,solid solution strengthening,dislocation strengthening and grain refinement of GNP and Ni.Among them,the strengthening effect of GNP on GNP-Ni/Cu composite is mainly load transfer strengthening and thermal mismatch strengthening,and the strengthening effect of Ni on GNP-Ni/Cu composite is mainly solid solution strengthening.This paper provides a theoretical basis and experimental reference for preparation of high-strength and high-conductivity CMCs. |
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