Micro-arc Oxidation Preparation Technology And Film Sealing Technology Of AZ80 Magnesium Alloy

Magnesium alloys have attracted much attention because of their low density,high strength,good casting properties,and their recyclability in automotive,chemical,aerospace and other fields.However,the high susceptibility to corrosion inherent in magnesium alloys limits their widespread application.MAO technology uses arc discharge to grow ceramic oxide film in situ on the surface of the substrate.The film has strong bonding force with the substrate,good toughness,high density,and has good wear resistance,corrosion resistance,high temperature resistance and insulation characteristics However,the high temperature and high pressure reaction in the film formation process will form a large number of hole structures on the surface,which provides a channel for the intrusion of corrosive media,which seriously affects the long-term protection of the oxide film layer.Therefore,micro-arc oxidation is studied.Process and sealing technology have become the current research focus.To this end,in this paper,the surface of AZ80 magnesium alloy after micro-arc oxidation treatment was surface-treated with different sealing agents,and a series of micro-arc oxidation and sealing composite films were prepared.Using X-ray diffractometer(XRD),scanning electron microscope(SEM),energy dispersive spectrometer(EDS),electrochemical workstation,friction and wear testing machine and other systems to study the effects of voltage,frequency,duty cycle and oxidation time on the micro-arc oxide film The effect of layer properties and microstructure,as well as the changes in the structure and properties of the membrane layer after sealing with polymethyltrimethoxysilane(PMTMS)and polytetrafluoroethylene(PTFE).The main research results are as follows:(1)In the alkaline phosphate electrolyte system,the corrosion resistance of the prepared MAO porous membrane layer is related to the surface porosity and roughness of the membrane layer.At voltage 350 V,frequency 700 Hz,duty cycle 10%,oxidation time Under the electrical parameters of 15 min,the surface porosity and roughness of the film layer are the smallest,and it has the best corrosion resistance and wear resistance.(2)Using different concentrations of PMTMS to seal the pores of the MAO film can effectively fill the pores and enhance the hydrophobicity of the film,It has little effect on the improvement of the wear resistance of the film.The films after 30 % mass fraction PMTMS sealing treatment showed the best corrosion resistance.(3)Sealing the MAO film with different concentrations of PTFE can effectively fill and coat the holes,enhance the hydrophobicity of the film,and significantly improve the wear resistance.The corrosion resistance and wear resistance of the membrane layer after 25 g/L mass concentration PTFE sealing treatment are the best.