| In order to meet the needs of social sustainable development,more and more attention has been paid to light metals and their alloys.7075 aluminum alloy is widely used in ship,aircraft and other important industrial fields because of its advantages of light weight,high strength,good toughness and hardness.However,the corrosion resistance of aluminum alloy in seawater environment is poor,which greatly limits its application.In this paper,micro-arc oxidation technology was used to prepare micro-arc oxidation ceramic film on the surface of 7075 aluminum alloy to improve the corrosion and wear properties of aluminum alloy materials.Then,both sol-gel technology and magnetron sputtering were combined with micro-arc oxidation to obtain different composite films.The electrochemical tests were used to analyze the corrosion resistance of composite films.The main research contents and conclusions of the thesis are as follows:（1）By micro-arc oxidation technology in the construction of micro-arc oxidation film of 7075 aluminum alloy surface as the typical"volcano"organization and appearance characteristics,compared with the aluminum alloy material,the surface roughness of the micro-arc oxidation film is larger,under the condition of dry friction the friction coefficient is higher,but the preparation of micro-arc oxide film with high hardness,good wear resistance,compared with the aluminum alloy material,The wear rate of microarc oxide films prepared in aluminate and phosphate electrolyte decreased by 87%and 92%,respectively.At the same time,the micro-arc oxidation film can significantly improve the corrosion resistance of aluminum alloy,especially the micro-arc oxidation film prepared by phosphate electrolyte has lower surface porosity and thicker film thickness,so it has better corrosion resistance.（2）Sol-gel technique can be used to improve the corrosion resistance of micro-arc oxidation film.The micropores on the surface of the micro-arc oxidation film were effectively sealed by the sol-gel film of silica.Compared with the uncoated ceramic film,the porosity of sol-gel/MAO composite film decreases from 8.10%to 2.27%,resulting in a decrease of more than one order of magnitude in the corrosion current density.The arc radius of the composite film is larger,and the impedance value of the composite film is about 20 times that of the single MAO film.After soaking in simulated seawater for five days,the composite film still has good corrosion resistance.（3）Titanium film was precoated on the surface of aluminum alloy by magnetron sputtering,and Ti O2/Al2O3 composite film was prepared by micro-arc oxidation.The surface of the titanium film is uniform and compact,and the thickness is about 710 nm.After micro-arc oxidation,the titanium film on the surface of aluminum alloy is completely oxidized to form Ti O2 phase consisting of rutile and anatase.The composite film is thicker and has fewer micropores on the surface,the porosity decreases from 8.10%to 1.06%,the corrosion potential of the composite film increases by 60 m V and the current density decreases by 1 order of magnitude compared with that of the single micro-arc oxidation film.Electrochemical impedance spectroscopy analysis shows that the composite film has a larger arc radius and a larger impedance value,so the composite film has the best corrosion resistance. |
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