Fabrication Of Aluminum Composite Foams Reinforced By Graphene And Their Compressive Properties And Deformation Behaviors

Aluminum(Al)foams have a combination of structural and functional characteristics such as excellent mechanical,electronical,thermal and magnetic properties,which make them attract a number of applications in the field of national defense,aerospace,rail transport and skyscraper industries.The research and development of high performance Al matrix composite foams(AMCFs)are imperative for the application in some severe demands.Graphene has a great potential as a reinforcement owing to its superior mechanical properties,but it is difficult to achieve a homogeneous dispersion in the AMCFs,restricting its application.The present work utilizes a template-assisted combined with high-temperature reduction approach to in-situ synthesize three-dimensional graphene decorated with copper nanoparticles(GNSs@Cu).Then,the GNSs@Cu and pure Al powder(or Al and Si mixed powder)are mixed through the ball-milling process.Finally,the “spaceholder method” and “powder metallurgy foaming method” are applied to fabricate the open-cell GNSs@Cu/Al composite foams and closed-cell GNSs@Cu/Al-Si composite foams,respectively.The effects of the GNSs@Cu on the macrostructure,microstructure,compressive and energy absorption property as well as deformation behavior of the composite foams are investigated.(1)“Space-holder method” is used to prepare the open-cell GNSs@Cu/Al composite foams with homogenously distributed of the GNSs@Cu.The effects of the ball-milling condition,GNSs@Cu content and relative density on the compressive and energy absorption property are studied.The results show that the compressive and energy absorption property of the open-cell composite foams increase first and then decrease with raising the GNSs@Cu content.The compression strength,plateau stress and energy absorption capacity of the 0.75 wt% GNSs@Cu/Al composite foams are supreme,which are advanced by 104.7%,113.7% and 115.1% through shift-speed ball milling process comparing with the pure Al foams,respectively.Besides,the open-cell composite foams with lower relative density possesses optimal energy absorption capacity for a wider range of compression stress with raising the GNSs@Cu content.(2)“Powder metallurgy foaming method” is used to prepare the closed-cell GNSs@Cu/Al-Si composite foams.The effects of the GNSs@Cu on the mechanical property,macrostructure and microstructure are studied.The results show that the hardness,the compressive and energy absorption property of the closed-cell composite foams are notable enhanced with the addition of the GNSs@Cu.The compression strength,plateau stress and energy absorption capacity of the 0.4 wt% GNSs@Cu/AlSi composite foams are advanced by 58.1%,53.8% and 51.1% comparing with the Al alloy foams,respectively.Moreover,the pore size,distribution and shape are prominent improved with the addition of the GNSs@Cu by changing pore nucleation sites and stabilizing pore growth.The eutectic Si phases are also modified with the addition of the GNSs@Cu by the way of impurity induced twinning mechanism.(3)The deformation behavior of Al(alloy)foams and AMCFs is studied and the deformation mode and strengthening mechanism are discussed.The results show that the compressive and energy absorption property are enhanced but the deformation modes are not changed with raising the GNSs@Cu content whether it is open-cell Al foams or closed-cell Al alloy foams.The open-cell composite foam exhibits a deformation mode in which the distortion zone expands layer by layer,while the closedcell composite foam shows the distortion propagation combined with the shear deformation mode.The above outcomes fully indicate the excellent strengthening and toughening effect of GNSs@Cu.