Fabrication And Mechanical Properties Of Graphene Reinforced Aluminum Matrix Composites By Melting Method

Graphene is an ideal reinforcement phase for metal matrix composites because of its unique structure and excellent mechanical properties and physicochemical properties.However,in the research of aluminium matrix composites,it was found that graphene has poor wettability with aluminium metal and is prone to agglomeration or structural damage during dispersion.On the other hand,the production rate of graphene/aluminum matrix composites by powder metallurgy is low and it is difficult to achieve large-scale production.Therefore,the research focus of this paper is to find an efficient method to prepare graphene/aluminum matrix composites with excellent mechanical properties.In this paper,freeze drying and spray drying technology combined with salt template method were used to prepare precursor of reinforcement respectively.Then two kinds of graphene reinforcements loaded with copper nanoparticles(Cu@GNP)with two structural characteristics were obtained by in situ chemical vapor deposition,and bulk composites were prepared by stirring melting and casting.The optimum technological parameters for preparing two kinds of reinforcements and composites were investigated;the effect of reinforcement content on the mechanical properties of composites was studied;the strengthening mechanisms of graphene reinforced aluminium matrix composites were explained by the characterization of the microstructures of composites.The results show that the morphology and structure of Cu@GNP can be adjusted by changing the ratio of raw materials.When the ratio of freeze-drying materials was Cu: C: Na=1: 3: 70 and the ratio of spray-drying materials was Cu: C: Na=1.5: 10:200,three dimensional continuous network graphene containing copper nanoparticles can be prepared.However,the reinforcement obtained by spray-drying method was spherical and smaller in size.In the process of stirring smelting,some copper nanoparticles can not react with the matrix,and improve the wettability of graphene and aluminum,so that the reinforcement can avoid agglomeration;some can react with aluminum matrix to form intermetallic compound transition phase,and strengthen the interface combination of the two.Through the mechanism of load transfer,dislocation produced by thermal mismatch,Orowan dislocation ring and fine grain strengthening,the reinforcement can improve the load transfer efficiency and ability,increase the dislocation density,hinder the dislocation movement and improve the mechanical properties of composite materials.The maximum tensile strength of Cu@GNP prepared by freeze-drying and spray-drying methods reinforced aluminum matrix composites increased by 55% and 76% respectively compared with pure aluminum.The graphene reinforced aluminum matrix composites were prepared by melting method.The efficiency of spray-drying Cu@GNP was lower,because its grain refinement and dislocation density increase were worse than the former's.