Study Of Aluminum Alloys Surface Coloring Technology By Micro-arc Oxidation And Its Power Supply

Coloring membrane in aluminum alloy surface is an important aspect of aluminum alloy surface treatment.The main methods of traditional are anodic oxide membrane adsorption of organic or inorganic dye coloring and direct anodic oxide coloring.However,according to these methods,the layer has color instability,poor wear resistance and corrosion resistance.Recently developing micro-arc oxidation technology is also a surface treatment technology,which placed aluminum alloy into electrolyte and then electrified in order to produce micro-plasma discharge,and then in the aluminum alloy surface,it will grow a ceramic membrane layer.Through this technology can get ceramic membrane which have high surface hardness,high heat resistance,good corrosion resistance, high adhesion,variety color,and stability color in the aluminum alloy surface.In this paper,it uses AC power mode to do four series micro-arc oxidation coloring technic experiment in aluminum alloy surface.Studied the influence of electrolyte composition and electrolyte parameters to surface quality of micro-arc oxidation coloring membrane.And make use of 631 micro-sclerometer to mensurate thickness and hardness of the coloring membrane.At the same time, we conduct a elementary research and analysis about the coloring principle of micro-arc oxidation coloring membrane.And brief analyse the development of micro-arc oxidation power supply and the influence of power supply parameters to the properties of ceramic membrane.On this basis,we compare the difference with AC power supply mode and bipolar pulse-bias power supply mode at ceramic membrane properties on the current micro-arc oxidation technicsThrough the experimental datas and phenomenon analysis indicates that:as Sodium as the main electrolyte can produce gray ceramic membrane;Use Sodium as the main electrolyte,and then add a mixture additives,Potassium hydroxide and Boric acid,can produce different colors in the ceramic membrane,the membrane color and surface quality will change happen with the different concentration of Sodium and mixture additives.The same as before,add coloring additives to the Sodium electrolyte,such as potassium ferricyanide or potassium hexacyanoferrate,can also produce colored ceramic membarne.However,the color of membrane is determined by coloring additive concentration,and Sodium concentration just influences the thickness and hardness of the membrane surface.In addition to the electrolyte parameters,the power supply modes and power supply parameters also have great impact on membrane properties.When make use of bipolar pulse-bias power supply mode to process workpiece,it usually can produce good property membrane.Because its power supply parameters,such as oxidation voltage,current density,pulse frequency,and pulse duty cycle,can be adjusted in a large-scale;in the same time,it has reverse low-voltage pulse,so can remove the loose layer of ceramic membrane surface when positive pulse processing workpiece.But AC power supply mode doesn't have this characteristic.In a word,use bipolar pulse-bias power supply mode can get better quality of ceramic membrane than AC power supply mode.However,the development of bipolar pulse-bias power supply is not sophisticated enough,it's still in the stage of research.So at the basis of previous,aim at the main circuit of bipolar pulse-bias power supply which mainly used in experiment,This article conduct a preliminary study and design...