Fabrication And Properties Of Aluminum/Graphene Composites

With the development of modern industry,how to prepare composites with good mechanical properties（plasticity,tensile strength,etc.）and excellent physical properties（electrical conductivity,thermal conductivity,etc.）has become a problem that researchers hope to solve.Aluminum matrix composites have good application prospects in many fields,such as power electronics and automobile manufacturing,due to low density,high strength-to-mass ratio and good conductivity.Graphene is a two-dimensional structural material closely arranged by a single layer of carbon atoms,which has excellent mechanical and physical properties.So graphene is an ideal reinforced material for composites.However,there are few researches on aluminum/graphene composites at present.In this paper,dispersion and preparation of aluminum/graphene composites were researched,different powders mixing processes were compared and analyzed,interface bonding states of composites prepared by different processes were researched.Subsequently,composites containing different graphene content were prepared by spark plasma sintering,the effect of graphene content on composites microstructure was observed,and the change of mechanical and physical properties of composites with graphene content was analyzed.The main conclusions are as follows:（1）Traditional ball milling method and V-type mixing method couldn’t disperse aluminum/graphene composites powders effectively.But wet mixing method was suitable for dispersion of aluminum/graphene composites powders,ultrasonic and mechanical stirring was an useful dispersion method.Graphene surface modification was effective to improve interface state of aluminum/graphene composites.Modified graphene（Ni-graphene）was coated with nickel-phosphorus alloy.Density difference between Ni-graphene and aluminum powders was smaller,so Ni-graphene was easier to disperse uniformly in aluminum powders.And porosity of composites was small,density of composites was high,due to interface bonding between Ni-graphene and aluminum matrix was well.（2）Interfacial reaction was slight in aluminum/graphene composites prepared by spark plasma sintering and canned extruded,interfacial diffusion layer was thin,and reaction product Al₄C₃ was not found at interface.Composites prepared by spark plasma sintering had fewer defects and higher density.In addition,with sintering temperature increase,composites interface changed from mechanical bonding to diffusion bonding,and diffusion layer thickness increased.With temperature increased further,aluminum melted,graphene agglomerated seriously in composites.（3）Graphene still maintained two-dimensional lamellar structure in composites.Graphene had a large contact area with aluminum matrix,which could effectively improve interface load transfer between aluminum matrix and graphene.When graphene content was low,the graphene dispersed uniformly in composites prepared by spark plasma sintering.With the content of graphene increase,graphene agglomerated more,and defects increased in composites.（4）A small amount of graphene can improve the comprehensive properties of aluminum/graphene composites.When graphene content was low,hardness and strength of composites raised with the increase of graphene content.Brinell hardness and tensile strength of 0.69 wt.%composites were 50.73 HB and 19.77 MPa,which were 8.20%and 42.41%higher than that of pure aluminum.However,the plasticity of composites decreased with the addition of graphene,composites elongation decreased from 23.77%of pure aluminum to7.53%of 0.69 wt.%composites.When graphene content was 0.30 wt.%,electrical conductivity of composites reached the maximum value of 56.81%IACS and thermal conductivity 248.41W/Km.