Effect Of Micro-arc Oxidation Film On Local Plastic Deformation Induced By Hydrogen In 7050 Aluminum Alloy

7050 aluminum alloy is a kind of high strength aluminum alloy with high strength,good electrical conductivity,very small density and good ductility.It is widely used in aircraft manufacturing,large ships,high-speed railway construction and other industrial fields.Under the combined action of stress and corrosive medium,7050 aluminum alloy parts in service are prone to stress corrosion cracking(SCC).Therefore,it is of great significance to find a method to improve the stress corrosion cracking resistance of 7050aluminum alloy.Micro-Arc Oxidation(MAO)is a new surface technology developed from anodic Oxidation technology,which has the characteristics of high efficiency,green environmental protection and simple process.By releasing high voltage current on the surface of aluminum,magnesium,titanium and other non-ferrous metals,it can generate high-quality ceramic film on the metal surface in situ.the mechanism of hydrogen embrittlement of aluminum alloys has always been controversial,and there are few studies on whether micro-arc oxidation film can inhibit the hydro-induced plastic deformation of aluminum alloys.Therefore,in this article,through adjusting the micro-arc oxidation voltage,nano TiO₂ additive concentration,oxidation time,and in 7050 aluminum alloy surface preparation of different micro-arc oxide film layer,constant displacement experiment was carried out in the humid air,combined with the hydrogen content analysis,scanning electron microscope,scanning electron microscopy,SEM),electrochemical testing,X-ray diffraction(X-ray diffraction,XRD),the following conclusions:(1)In the wet air with RH=80%,the micro-arc oxidation film can effectively inhibit the local plastic deformation of 7050 aluminum alloy and improve the corrosion resistance of aluminum alloy.(2)When the constant displacement high-strength aluminum alloy sample is placed in wet air,the plastic zone at the crack tip will increase with the extension of time with the entry of hydrogen.(3)The corrosion resistance and compactness of MAO aluminum alloy samples prepared by different micro-arc oxidation voltages increased firstly and then decreased.When the micro-arc oxidation voltage is 450 V,the film has the best densification and corrosion resistance.(4)The film thickness of MAO aluminum alloy samples prepared with different micro-arc oxidation time increased with time,but the densification and corrosion resistance increased first and then decreased.When the micro-arc oxidation time was 12 min,the film densification and corrosion resistance reached the best.(5)The addition of nano-TiO₂ additive can increase the amount of?-Al₂O₃ in the micro-arc oxidation film,and can react with Al₂O₃ to improve the film density.When the concentration of nano-TiO2 additive is 10 g/L,the film is the densest,and the measured K_ISCC of aluminum alloy is 27.05MPa·m^1/2.