Study Of Preparation And Properties Of Graphene And Graphene Reinforced Al-Mg-Si Composites

Graphene has been given excellent physical and chemical properties because of its unique two-dimensional structure.At present,graphene is difficult to achieve high-quality,large-scale production has severely inhibited its broad application prospects.In this paper,graphene was prepared by DC arc method.By changing the pressure and atmosphere of the plasma,the influence of arc discharge on the growth of graphene was studied,in order to optimize the process parameters for the preparation of graphene by DC arc method.The different pressures of the plasma were made using argon as a buffer gas,and the plasma atmosphere was formed by mixing argon gas with hydrogen and nitrogen at the same ratio?3:97?,respectively.Graphene/Al-Mg-Si composite was prepared by FADB method with graphene as the reinforcement and Al-Mg-Si alloy as the matrix.The effects of the amount of graphene on the microstructure and properties of the composites were investigated.Graphene has the same surface morphology under different pressures and atmospheres,and the flake surface structure is full of wavy folds,which change from two-dimensional structure to three dimensional direction.Graphene sheets overlap each other,showing a multilayer structure.Under the negative pressure environment,there are fewer defects than the positively pressed graphene,but under the negative pressure,the number of graphene layers fluctuates more than the positive pressure.When the pressure is-0.03 MPa,the values of I_D/I_G and I_G/I_2D of graphene are 0.68 and 1.74,respectively,and the thickness is about 0.34nm to 2 nm,and the number of layers fluctuates from single layer to five layers.When the pressure is 0.06 MPa,the values of I_D/I_G and I_G/I_2D of graphene are 1.05and 1.77,respectively,and the thickness is concentrated at about 2 nm,which is mainly a 5-layer structure.The quality of graphene prepared in the presence of hydrogen in the plasma atmosphere is higher than that in other atmospheres.The values of I_D/I_G and I_G/I_2DD are 0.54 and 1.53,respectively,and the number of layers is mainly double,indicating that the hydrogen atmosphere is conducive to the growth of graphene.When nitrogen was present in the plasma atmosphere,the formation of a large amount of amorphous carbon was found,indicating that the presence of nitrogen suppresses the growth of graphene.The phase of the graphene/Al-Mg-Si composite is mainly composed of Al,Si,Mg₂Si phase and graphene,and no harmful phase Al₄C₃ is formed.Graphene can refine the matrix grains and promote uniform distribution of Si grains.In the graphene/Al-Mg-Si composites,the graphene-matrix interface is well-bonded,and it is mainly bonded along the grain boundary and surface and bonded to the matrix.The graphene is dispersed evenly and no serious agglomeration occurs.The hardness and tensile strength of the composite increase first and then decrease as the graphene content increases.When the addition of graphene is 1.5%,the hardness of the composite reaches a maximum of 121.7 HV,which is 49%higher than that of the matrix.When the addition amount of graphene reaches1.0%,the tensile strength is as high as 293 MPa and the strength is about twice that of the matrix.There is no obvious“necking”phenomenon when the composite material is broken.The crack source is mainly the tearing ridges and pits formed by the fracture and desorption of graphene.The main strengthening effects of graphene in composites include grain refinement,dislocation strengthening,load transfer,and Orowan reinforcement.