| Graphene has a variety of amazing mechanical and physical properties, recent research on graphene reinforced composites proved the feasibility of making graphene as reinforcement to improve the properties of composites. Current research on graphene reinforced metal matrix(especially aluminum) composites are gradually increasing, but it still has many problems. According to the research status,this paper mixed powder by ball milling, prepared GNPs /6063 Al composites by pressure infiltration. Moreover, the composites extrusion and rolling deformation process has been done. The microstructure of the original materials, GNPs-Al mixed powders and composites were investigated by optical microscopy, SEM, TEM, XRD,Raman spectroscopy, XPS and the other analysis methods. The mechanical, thermal physical properties of the composites were tested.Ball milling can make graphene evenly dispersed in the matrix powder,graphene distributed between aluminum particles and coated on the outer surface of the particles, some graphene has compound into to the interior portion of the large particles to form composite particles. The mechanical properties of composite contacted with the milling time, 1.8wt% GNPs / 6063 Al composite with 12 h milling time has the best performance, it`s elastic modulus reached 84 GPa, T6 state tensile strength 294.7MPa, yield strength 170.9MPa, after 13:1 extrusion.With the increase of the content of graphene, the dispersion of graphene will be more difficult, it will increased material defects, the modulus of cast composites show a downward trend. Below 1.8 wt. % content, the tensile strength and yield strength of composite increased with the increase of graphene content, after 13:1extrusion. 1.8wt.% composite reached the maximum, T6 state tensile strength294.7MPa(18% increase compared to the matrix), yield strength 170.9MPa(47%increase compared to the base). When the content exceeds 1.8wt.%, the yield and tensile strength began to decline. In addition, graphene has no contribute to improve the plastic of composite.Deform processing can greatly improve the mechanical properties of the casting composite, after 6.4:1+13:1 extrusion and rolling process, the yield and tensile strength of 1.8wt%GNPs/6063 Al composite reach the maximum,T6 state yield Strength 273.4MPa, tensile strength 337.4MPa. And after 6.4:1+13:1 extrusion,the bending strength of composite achieved the highest value 576.3MPa. In addition, deform processing can greatly improve the plastic of composite.It can be proved that deform processing lead to grain refinement, organization homogenization, graphene decentralization by SEM, TEM analysis. The interlayeropening and directional arrangement of graphene also be observed.A new method to characterize graphene layers by Raman spectroscopy has been proposed.Established shear hysteresis model to explain graphene Strengthening mechanism. Improving graphene distribution, using matrix which has higher shear yield strength, and thinner graphene which has larger diameter, the strengthen efficiency can be improved. For certain content composite, the yield strength increases while the number of graphene layers decreases, single-layer graphene composite has the highest yield strength in theory. When 4.46 vol.% GNPs / 6063 Al composites are single-layer graphene composite, it`s theoretical yield strength reach360 MPa.The thermal conductivity of casting composite decreases while graphene content increases, it will be obviously improved after extrusion process. The thermal conductivity of the composites will remain at 170W/(m·K), no matter the change of graphene content. The thermal expansion coefficient of composite will decrease when graphene content increase, and decrease more after extrusion, the thermal expansion coefficient of the 4.2wt.% composite has dropped to about 1.8×10-5K-1. |
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