| As the lightest type of metal structural material,magnesium alloy not only has high specific strength,but also has high rigidity and ideal processing performance.At present,magnesium alloys are highly favored by the industry due to a series of advantages such as excellent electromagnetic shielding,outstanding impact resistance,and excellent welding properties.Application,it is regarded as the first choice for electronic product housing materials and light vehicle steering system materials.However,although magnesium alloy has many outstanding advantages,it also has some defects that cannot be ignored,such as poor plasticity and low elastic modulus,which effectively restricts the further expansion of its application range.Research has found that surface coating is a common and effective way to improve the mechanical properties of magnesium alloys.In this paper,the electrodeposition method is used to uniformly composite carbon nanotubes into the metal aluminum coating,so that the coating is composed of a continuous phase of matrix metal and a dispersed phase.It is composed of nanoparticles.The formation of the composite coating helps to improve the various properties of magnesium alloys,and enhance the mechanical properties and corrosion resistance of magnesium alloys.By preparing the aluminum-carbon nanotube composite coating on the surface of the magnesium alloy,the density of the aluminum coating composite material can be reduced,which not only meets the demand of lightweight magnesium alloy in actual use,but also improves the mechanical properties of the magnesium alloy and enhances the corrosion resistance of the magnesium alloy To expand the scope of application of magnesium alloys.In this paper,magnesium alloy is used as a substrate,organic solvent system is used,benzene and tetrahydrofuran are used as solvents,and carbon nanotubes are used as nano-reinforcing materials to prepare aluminum-carbon nanotube composite coatings.Scanning electron microscope(SEM)and energy spectrum analysis(EDS)are used.),X-ray diffraction phase analysis(XRD),Raman spectroscopy(Ranman)to characterize and analyze the microscopic morphology,composition and structure of the aluminum-carbon nanotube composite coating,and detect its microhardness and friction coefficient,Roughness,wear rate,elastic modulus,corrosion resistance,coating thickness.(1)The micro morphology of the composite coating was characterized by SEM,and it was confirmed that aluminum and carbon nanotubes were co-deposited on the substrate.Compared with the pure aluminum coating,the surface grain of the composite coating was refined and the porosity was low.The composition of the composite coating was analyzed by EDS energy spectrum.The results showed that the aluminum-carbon nanotube composite coating was mainly composed of three elements:Al,C,and O,and the elements were evenly distributed,indicating that the carbon nanotubes were evenly embedded in the coating.In addition,the XRD test results of the coating show that the diffraction peak of the composite coating is wider than that of the pure aluminum coating,indicating that the crystal grain size of the composite coating is smaller than that of the pure aluminum coating.Addition reduces the grain size of the coating from 25.53nm to 16.68nm.(2)Through orthogonal experiments on the concentration of carbon nanotubes,current density,and stirring rate,with microhardness and friction coefficient as performance indicators,the best experimental conditions are:carbon nanotube concentration 1g/L,current density 4A/dm2,stirring rate 250r/min,electroplating time 45min,the microhardness of the coating under this condition is 156.5HV,the friction coefficient is 0.56,compared with pure aluminum coating(67HV)and magnesium alloy substrate hardness(55HV),composite coating The hardness increased by 1.34 times and 1.85 times respectively.Compared with the friction coefficient of pure aluminum coating(0.74)and magnesium alloy substrate(0.64),the friction coefficients are reduced by 24.3%and 12.5%,respectively.The order of the influence of process parameters on the microhardness of the aluminum-carbon nanotube composite coating is:current density>carbon nanotube concentration>plating time>stirring rate,and the order of influence on the friction coefficient is:carbon nanotube concentration>current density>stirring rate>Plating time.(3)Through single factor experiments,the effects of carbon nanotube concentration,current density,and stirring rate on the microhardness,friction and wear,surface roughness,and coating thickness of the composite coating were explored.The maximum microhardness detected is 171.2HV,the minimum surface roughness is 0.93μm,the minimum friction coefficient is 0.54,the minimum wear rate is 1.32μm and the maximum coating thickness is 32.8μm.(4)Analyzing the AC impedance diagram of the coating and magnesium alloy substrate,it can be seen that when the concentration of carbon nanotubes is 2g/L,the composite coating has the best corrosion resistance.Compared with pure aluminum coating and magnesium alloy substrate,it is corrosion resistant.Performance is greatly improved.Put the pure aluminum coating and the aluminum-carbon nanotube composite coating into neutral,acidic,and alkaline corrosive media,respectively,and test the Tafel curve.It can be seen that the composite coating is more resistant to neutral and acidic media compared to pure aluminum coating.Corrosion performance is good,but in alkaline medium,corrosion resistance is poor. |
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