Preparation And Properties Of Aluminum Matrix Composites Reinforced With Graphene

As a two-dimensional structure carbon group material,graphene has excelle nt mechanical and physical properties,which can be used to prepare graphene/alumi num matrix composites with high strength,high conductivity and high thermal conductivit y.However,graphene is prone to agglomeration,interface reaction with matrix and poor wettability.In order to solve the above problems,the G/Al composites and GA/Al composites were prepared by high-energy ball milling and Spark Plasma Sintering(SPS)technology,and the mechanical,electrical and thermal properties of the composites were studied.It is generally believed that the higher the vacuum degree,the better the sintering result.Therefore,the influence of vacuum degree(orders of magnitude of 10⁰,10^-1 and10^-2 Pa)on the composition and mechanical properties of active metal(Al,Cr,Ti)prepared by SPS was studied,which provides a basis for the selection of vacuum degree in the preparation of aluminum matrix composites of SPS.Active metal materials with different vacuum degrees were prepared by SPS.Firstly,it was found that the content of nitrogen and oxygen in the active metals prepared under different vacuum degrees decreased compared with the original powders,but the improvement of vacuum degree had no obvious effect on the removal of nitrogen and oxygen in the active metal.The XPS results showed that the nitrogen and oxygen removed in the active metals was the free nitrogen and oxygen in the original powders.Secondly,the enhancement of vacuum degree has no effect on the density,hardness,tensile strength and fracture form of the active metal.In conclusion,the vacuum degree of 100 Pa order of magnitude has met the requirements for the preparation of SPS for active metals.Graphene was pre-dispersed by a cell fragmentation apparatus,and the dispersed graphene showed good dispersion in deionized water solution.The G/Al composite powder was prepared by high-energy ball milling.The optimal parameters of ball milling were rotation speed of 350 rpm,ball milling time of 6 h(run 5 min,stop 10 min)and weight ratio of ball-to-powder of 5:1.The composite powder was laminated,and the graphene was evenly distributed and could be adsorbed on aluminum powder.The effects of different sintering temperatures and different graphene models on the mechanica l properties and electrical conductivity of G/Al composites were studied.It was concluded that the optimum sintering temperatures of SPS was 600?and 3#graphene had better strengthening effect.G/Al composites with different mass fractions of graphene were prepared under the conditions of sintering pressure 50 MPa,sintering temperature 600?,holding time 10 min and gradient heating.The relative density of the composites were all above 98.85%.0.3wt.%G/Al composites have the optinal mechanical and electrical properties,which the vickers hardness,tensile strength and conductivity are 35.3 HV,77.7MPa and 19.9 m S/m,respectively.And the vickers hardness of composites was 13.5%higher than that of pure aluminum prepared by SPS.GA/Al composites were prepared by aluminum coated grapheme(GA).GA/Al composites with high relative density and different mass fractions were prepared by the same ball milling and sintering processes as those for G/Al composites.The vickers hardness of 3wt.%GA/Al composites was 47.6 HV,which was 53%higher than that of pure aluminum(31.1 HV).The tensile strength of 2.5wt.%GA/Al composites was 118.4MPa,which was 21.3%higher than that of pure aluminum,but the elongation was lower than that of pure aluminum.The electrical and thermal properties of the composites show the characteristics of anisotropy,in which the axial conductivity is higher than the radial conductivity,and the radial thermal conductivity is higher than the axial conductivity.The axial conductivity and radial thermal conductivity of the 2.5wt.%GA/Al composites are29.2 m S/m and 201.5 W/(m K),respectively.