Fabrication And Properties Of Aluminium Matrix Composites Reinforced With Reduced Graphene Oxide

Graphene has proved to be a promising reinforcing phase of metal matrix composites due to its unique structure and excellent mechanical,thermal properties.In this paper,in order to investigate the application of graphene in reinforcing aluminum matrix composites,we introduced a novel method,solution-mixing,to distribute graphene into the Al matrix.Combined with powder metallurgy and hot extrusion,aluminum matrix composites reinforced with graphene were fabricated.The tensile properties were tested by tensile experiments and the strengthening mechanism was also discussed.In addition,hybrid aluminum matrix composites consisting of SiC particles and graphene were fabricated by a combination of Solution-mixing and Powder metallurgy route.The friction and wear properties of the hybrid composites were studied by using a ball-on-disc tribotester.The effects of graphene content,load on the wear resistance of the hybrid composites were evaluated in detail.Also the relevant wear mechanisms were studied.An improved Hummers' method was selected to fabricate Graphene which shows few layers and high quality.The solution-mixing method proved to be an effective method to disperse graphene uniformly in the Al matrix.The results of tensile tests showed that the tensile strength and microhardness of Al/Graphene composites were improved greatly with the addition of graphene.The tensile strength and hardness were 255 MPa and 74.3±2.9(HV)respectively with only0.3wt.% graphene,as well as the elongation of 19.2%;when the graphene content increased to 0.6wt.%,the tensile strength and hardness decreased slightly and the elongation decreased to 13.2%.By analyzing the microstructure of Al/graphene composites,the main strengthening mechanisms are fine grain strengthening and dislocation strengthening.The micro-hardness results of the hybrid composites showed that the hardness of the hybrid composites was higher than that of Al/SiC composites.With the increase of graphene content,the micro-hardness increased first and then decreased.When the graphene content was 0.3wt.%,the hybrid composites showed the maximum micro-hardness value.The results of dry sliding wear tests showed that the average coefficient of friction of all composites decreased first and then increased with the increase ofnormal load,and the wear rate increased with the increase of load.Compared with the Al-Si/SiC composites,the hybrid composites exhibited a lower wear rate and a higher critical load.The hybrid composites with 0.5wt.% graphene showed a more stable coefficient of friction and a lower wear rate in the range of 1-3.2N.When the graphene content increased to 0.7wt.%,the wear rate at 2.5N increased rapidly,which means the appearance of critical load.By analyzing the macrographs and micrographs of the worn surfaces and debris,the dominant wear mechanism for Al-Si/SiC composites was delamination wear in the range of 1-3.2N.While the main wear mechanism for hybrid composites was abrasive wear accompanied with adhesion wear at low loads,delamination wear became the main wear mechanism at high loads.