Research On Bionic Construction And Performance Of Micro-nano Structure On 6061 Aluminum Alloy Surface

Aluminum alloys have a series of advantages,such as low density,good weldability,easy forming and high mechanical strength.They are widely used in aerospace,machinery manufacturing,bioengineering,modern medicine,military,energy environment and daily life.In recent years,the development of biomimetic functional materials provides a new way to improve the performance of metal surface.In this research,6061 aluminum alloy was selected as the research object,combined with the existing bionic model,the bionic structure was constructed by electrochemical technology.The friction reduction and drag reduction performance of convex and unsmooth surface were studied.The wettability of hydrophobic structure on aluminum alloy surface was studied as well.The conclusions are listed as follows:(1)6061 aluminum alloy was anodized and then Ni-P coating was electrodeposited on the oxide film to form a convex and unsmooth surface.The experimental parameters affecting the surface morphology of the coating,such as the pretreatment of the substrate,the pore size of the alumina nanotubes,the current density of the electrodeposition,the temperature of the plating solution and the electrodeposition time,were regulated.The results show that the pretreatment method has a decisive influence on the surface morphology of the coating.The coating which utilized the second zinc dipping treatment is smooth,while the coating which utilized the anodizing treatment is convex and unsmooth.The pore diameter of the anodised alumina nanotubes and the current density of the electrodeposition are the main factors,while the temperature of the plating solution and the time of the electrodeposition are the secondary factors.(2)The surface morphology,microstructure and properties of the coating were tested by microhardness tester,scanning electron microscope,X-ray diffractometer,wear tester and electrochemical workstation.The results show that the surface of the coating presents a hemispherical convex shape with uniform distribution.The microhardness of the Ni-P coating is 612 HV,which is 6 times higher than that of the aluminum alloy matrix.Compared with the ordinary coating with smooth surface,the average friction coefficient of the convex non smooth surface is reduced by more than 40%,and the wear volume is reduced by about 52%.Compared with the Electrodeposited coatings,the anodic oxidation electrodeposition forms dual protection by oxidation film and coating,and the corrosion rate is reduced by76%.The porous structure of the anodic oxidation film plays a role of "pinning" on the surface coating,and the adhesion of the coating on the convex unsmooth surface is obviously better than that on the smooth surface coating.(3)Porous nanotubes were formed on the surface of aluminum alloy by anodizing,and Ni layer was electrodeposited on the oxide film to form a hydrophobic surface.The results show that the nano structure with petal like spots on the surface of alumina has a maximum contact angle of 148°.Compared with the naturally formed oxide film surface,the hydrophobicity is improved by 23%,and the corrosion rate is reduced by more than two times.Ni layer was electrodeposited on the convex and unsmooth surface for a short time to construct micro-nano structure.The results show that the Ni layer on the unsmooth surface has a nano needle shape.The superhydrophobic effect was achieved after modified by low-energy materials.The contact angle of the surface is more than 150° and the rolling angle is less than 10°.The corrosion rate of the surface with superhydrophobic structure is68% lower than that of the convex unsmooth surface without micro-nano structure.