Study On Microstructure And Wear Properties Of Graphene Reinforced Aluminum Matrix Composites

In this paper,using 7075Al alloy powder as matrix,graphene,graphene/SiC hybrid,graphene-coated SiC and copper-plated graphene as reinforcement phase,the composite powder of aluminum alloy and reinforcement phase was prepared by high energy ball milling.After hot pressing and sintering,the final aluminum matrix composites were obtained by solid solution and aging treatment.Firstly,7075Al alloy and graphene reinforced aluminum matrix composites were characterized,and the sample density was measured by Archimedes drainage method.The interface was well bonded and there was no Al₄C₃ formation by XRD,SEM and EDS analysis.Through the tests of tensile strength,yield strength,elongation and hardness,it is found that the properties of aluminum alloy matrix are improved by the addition of graphene.When the mass fraction of graphene reaches 1.0wt%,it is 60.5%,20.3%,298.2%and 30.4%higher than that of 7075Al alloy.Among them,through the fracture SEM analysis,the increase in the number of dimples shows that the plasticity of the material has changed.The friction and wear experiments show that with the addition of graphene,the friction coefficient and wear rate of the matrix are reduced,the effects of adhesive wear and delamination wear are gradually disappeared,and the wear cross-sectional area is also gradually reduced.This is because graphene shares the load to a certain extent and uses its own lubrication to reduce the friction resistance and improve the wear resistance of the material.Graphene and SiC were added to the matrix at the ratio of 1:1 to form hybrid reinforced composites.The density of hybrid composites was lower than that of graphene composites with the addition of SiC phase,but the overall properties were improved.When the mass fraction of the two reached 0.75wt%respectively,the properties of the hybrid reinforced composites reached the best,and the tensile strength,yield strength,elongation and hardness reached 323.04MPa,201.86MPa,3.75%and142.54 HV.Among them,the fracture dimples were finer and the toughness was improved by SEM analysis.The friction and wear test at this time shows that the friction coefficient and wear rate decrease again,there is a small amount of adhesive wear,and the wear cross-sectional area is smaller.This is because the addition of hybrid reinforcement phase refines the grains,the increase of grain boundaries hinders the dislocation movement,and the high hardness of SiC particles protects the matrix alloy from wear to a certain extent,thus improving the wear resistance of the material.Graphene-coated SiC and copper-plated graphene aluminum matrix composites were prepared by using the optimum ratio parameters of hybrid composites.Through the observation of SEM and 3D micrographs of the worn surface,the wear properties of the two groups of composites are better,the core-shell structure of SiC and graphene is coated,and the problems of graphene and SiC particles are solved at the same time.Copper-plated graphene reinforced aluminum matrix composites release the stress acting on the surface into strain through its flake structure,and the copper particles attached to the surface as rolling bearings can effectively reduce the friction resistance in the friction process.