Study On Preparation And Properties Of Carbon Nanotubes Reinforced Aluminum Matrix Composites

Aluminum alloys are widely used for its low density,high strength,good wear resistance and good corrosion resistance.However,modern industry and science and technology are developing more and more rapidly,and the requirements for material properties are getting higher and higher.Traditional aluminum alloy materials can no longer meet the needs of social development.Carbon nanotubes are an ideal reinforcement for metal composites because of its unique structures,good mechanical,thermal and other properties.In this paper,7075 aluminum alloy were used as the matrix material,and CNTs were used as the reinforcing phase.Single aluminum alloy and CNTs/7075Al composites have been prepared by SPS process.The fracture morphology,composition and microstructure of the composites were characterized by SEM,EDS,XRD and Raman spectrum.The optimal process parameters were determined by comparative analysis.The effects of different process parameters on the density,hardness,elastic modulus,wear resistance and corrosion resistance of the composites were studied,and compared with single aluminum alloy material.The results show that:?1?The optimum sintering conditions for CNTs/7075Al composites are as follows:sintering temperature is 550?,the content of carbon nanotubes is 2wt%,the holding time is 6min,the axial pressure is 50MPa,and the heating rate is 50?/min.The density of the composites prepared under this condition is 94.7%,which is lower than that of single aluminum alloy.The hardness is 129.5HV,which is 15.5%higher than single aluminum alloy material,The average friction coefficient is0.4365,and the wear rate is 1.98×10^-5mm³/N?m,which is 37.5%and 43.3%lower than that of single aluminum alloy material,and the elastic modulus is 121.5 GPa,which is 39.3%higher than the single aluminum aloy material.?2?Raman spectral analysis proved the existence of CNTs in the composites.No aggregates were found in the fracture of the sample through SEM observation,and CNTs were uniformly dispersed in the aluminum alloy matrix and formed a good bonding interface with the matrix material.The peak of Al₄C₃ in XRD pattern is weak,and Al₂O₃ was not found.?3?The addition of CNTs can significantly improve the hardness,friction and wear,elastic modulus and other properties of aluminum alloy composites,But the density of composite material is lower than that of single aluminum alloy.As the content of CNTs increases,the hardness and elastic modulus of the composites generally increase first and then decrease,the coefficient of friction and wear rate decrease first and then increase.With the increase of sintering temperature,the density and hardness of the composites increase first and then decrease,and the friction coefficient and wear rate decrease first and then tend to be stable.In addition,with the increase of holding time and heating rate,the hardness increases first,then decreases and gradually decreases.With the increase of axial pressure,the compactness of composites becomes better and better.?4?The corrosion products of the two materials appear at different times.Corrosion products appear earlier on the surface of the composite material.However,with the extension of corrosion time,the corrosion rate of composite material decreases,and the corrosion resistance is better than that of single aluminum alloy material.The composite with a sintering temperature of 550°C has the best corrosion resistance and a corrosion resistance rating of 4.Compared with the corrosion resistance of a single aluminum alloy material,it has some improvement.The addition of CNTs prevents the concentration of corrosion defects in the material and improves the corrosion resistance of the composite to some extent,but it also destroys the continuity of the oxide film on the surface of the composite.The formation process of corrosion products of the two kinds of materials is different.The single aluminum alloy material is mainly developed by flake corrosion,and the aluminum alloy composite material is mainly developed by pitting corrosion.By analyzing the energy spectrum,we found that the corrosion products are mainly aluminum,oxygen,magnesium,zinc and chlorine.The hardness of the composite after corrosion is 89.8 HV,which is 30.7%lower than that before corrosion.