Fabrication And Properties Of Aluminum/Cu-graphene Composites

Graphene,which has excellent mechanical and physical properties,is a new type of reinforcement material with great potential.However,the poor wettability with aluminum and difficult dispersion of graphene limited the development of graphene/aluminum composites.In this subject,the graphene surface was firstly modified to improve the interface wettability of graphene and aluminum.Then the graphene was dispersed by a combination of ultrasonic treatment and mechanical stirring to reduce the agglomeration.Finally,the low temperature sintering fabrication of the graphene/6061 Al composite was conducted by spark plasma sintering process.This article explored the effect of graphene surface modification on the dispersion of graphene in aluminum and their interface bonding.The effect of graphene sheet diameter and content on the mechanical and physical properties of the graphene/6061 Al composite was studied as well.The main conclusions are as follows:(1)The surface modification of graphene is beneficial to the dispersion of graphene as well as improving the interface bonding between graphene and aluminum.After surface modification treatment,the surface of graphene is attached with metal particles,leading to a much smaller difference in density between the modified graphene and aluminum powder,which is beneficial to the uniform dispersion of graphene in aluminum powder.The dispersion effect of the copper-plated graphene is well.(2)The combination of ultrasonic dispersion and mechanical stirring method performs well in the dispersion of graphene and the dispersed graphene maintains a two-dimensional gauze shape in the aluminum powder.When the graphene is mixed with aluminum powder with different particle sizes,the aluminum powder with smaller particle size possesses better dispersion effect.Moreover,when mixed with aluminum powder with the same particle size,graphene with smaller sheet diameter shows better dispersion effect than the larger sheet diameter one.(3)The copper-plated graphene/aluminum composite fabricated by the spark plasma sintering process possess higher efficiency of space filling and fewer pores as well as a uniform dispersion of graphene.Graphene in the composite has semi-transparent fold morphology and the interface with aluminum shows diffusion bonding characteristic.Copper on the copper-plated graphene surface reduces the direct contact area between graphene and aluminum,and diffuses into the aluminum matrix after sintering,strengthening the interface bonding between graphene and aluminum.Moreover,copper on the surface of graphene has little direct contribution to the enhancement of the mechanical properties of the composites.Instead,by strengthening the interface boding between graphene and aluminum the copper improves the enhancement efficiency of graphene,thus enhancing the mechanical properties of composites.(4)The addition of a small amount of graphene can improve the overall performance of the composite.The hardness and tensile strength of the composite increase with the increase of the graphene content when the mass fraction of graphene in composites is less than 1%.The tensile strength and hardness of the composite reached the maximum values of 227.14 MPa and 68.84 HB when the mass fraction of graphene in composites is 0.75% and 1% respectively,accompanied by the continuous reduction in elongation.The electrical conductivity and thermal conductivity of composites reached the maximum value of 46.55% IACS and 163.58W/(m·K)when the mass fraction of graphene in the composite is 0.5% and 0.75%,respectively.(5)Graphene with two different sheet diameters can both improve the comprehensive properties of the composite.Graphene with two different sheet diameters have different effects on the mechanical properties of the composite,which is related to the enhancement mechanisms.The graphene with larger sheet diameter is more conducive to achieving the balance between strength and plasticity.Graphene with two different sheet diameters have different effects on the physical properties of the composite,which is related to the distribution of graphene in the composite.In a word,the graphene with larger diameter has a better effect on enhancing the comprehensive properties of the composite.