| Aluminum and its alloy are widely used in industry. But their application is limited by their low surface hardness, poor wear-resistance and poor anti-corrosion to the solution of halide and inorganic acid. To improve the surface capability of aluminum alloy, we can treat its surface by using surface painting, thermal spraying, PVD, electroplating, chemical transform film, electrochemistry oxidation and so on surface treatments. Among them, the technology of anodic oxidation is often used. The basic principle of anodic oxide technology is that aluminum or its alloy is electrochemistry oxidized as positive in the alkaline or acid electrolyte; then the oxidation film can be formed, which has excellent machinery and corrosion-resistance properties. Oxide-film is mainly composed of amorphous oxides.Micro-arc oxidation is also called micro-plasma oxidation or positive spark deposit technology. It is a new surface treatment technique, which is developed from anodic oxidation. By micro-plasma discharging, through complex electrochemistry, plasma-chemistry and thermal-chemistry processes, ceramic oxide-film is created on the surface. The thickness of ceramic oxide-film that created by micro-arc technology can be up to 200-300 H m, the micro-hardness can be over HV2000, which extends the application range of aluminum alloy.By a series of micro-arc oxidation experiments, I have studied the law of the growth of ceramic oxide-film, such as the action of different composition and concentration of electrolyte influence on the growth of ceramic oxide-film, and the influence by the voltage between electrodes, current density and oxidizing time. Using SEM and XRD, I have analyzed the micro-shape and fabric of ceramic oxide-film, and tested the capability of anti-heat-impact, anti-corrosion, and anti-external strike of ceramic oxide-film.The photos of SEM show that ceramic oxide-film is made up of two layers, the external porous layer and the internal denser one. The denser layer is as about 2/3 thick as the whole layer. The analysis using XRD points out that there are gamma-Al2O3 and alpha -Al2O3 crystal in the ceramic oxide-film. The more oxidizing time the more a -IVIf we heat treat the ceramic oxide-film by 500℃×60min treatment, gamma-Al2O3 will increase.The capability tests show that oxide-film has excellent anti-heat strike ability. The oxide-film surface still no slight crack after ten times of 600 ℃ -25 ℃ rapid cooling-rapid heating impact. The anti-corrosion of oxide layer is very good. At 20℃, when it is placed in 10%NaCl solution, 10%Hcl solution, 10%NaOH solution, the samples don't lose their weight within the measure range of the scale. The small opening on the ceramic film will decrease the surface anti-corrosion ability, but which will be greatly improved after being sealed. Its ability of anti-external strike is strengthened too, but the mechanical property of the aluminum alloy matrix restricts the anti-external strike ability of the oxide-film. The micro-hardness of ceramic oxide-film can be up to HV1800 at most.Experimentations indicate that the process of growth of ceramic oxide-film has six phases: 1. Creating of surface obstruction film. The surface of sample quickly forms a dense amorphous oxide-film. 2. Electro-puncture of obstruction film. Through increasing the voltage between electrodes, obstruction film is punctured by electricity, and spark discharge happen. 3. Growth of amorphous oxide-film. Because the voltage between electrodes and current density is low, spark discharge is weak; so less ceramic oxide is found, mainly more amorphous oxide-film grows. 4. Creating of local ceramic oxide-film. By the action of high temperature and high-pressure that produced by micro-plasma discharge, amorphous oxide-film melts quickly, then freezes quickly by the action of cool electrolyte. Amorphous oxide melts into ceramic oxide-grain, which contains y-Al2O3 and a-Al2O3 crystal. Oxide-grain grow successively, and it joins the neighborhood Oxide-grains. The local ceramic oxide-film creates. 5.
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