本科生毕业设计（论文）专业外文翻译原文：Magnesium alloy electric wheel hubmicro-arc oxidation production research 译文：镁合金电动车轮毂微弧氧化生产研究指导教师：张清郁职称：讲师学生姓名：陈孟丽学号：1002130301专业：机械设计制造及其自动化院（系）：机电工程学院2015年4月10日Magnesium alloy electric wheel hub micro-arc oxidation production researchMost electric vehicles at home and abroad is configured to aluminum alloy wheel hub, its quality, energy saving, shock absorption, noise reduction and vehicle dynamics characteristics index is much lower than magnesium alloys. Magnesium alloy is 30% lighter than aluminum alloy, the damping effect is 30 times that of aluminum alloy. Replace the aluminum alloy with magnesium alloy wheel hub, driving the development of magnesium alloy material development and deep processing technology, to reduce electric vehicle weight and power consumption, energy conservation and environmental protection; To reduce vibration and noise; Improve ride comfort and electric vehicle dynamic characteristics such as objective (transportation quality each reduce 10%, energy consumption will be reduced 8% ~ 10%). But its corrosion resistance is poor, seriously limits the application. Commonly used chemical oxidation and anode oxidation formation of oxide film on magnesium alloy has certain protective effect, but its corrosion resistance, environmental friendliness, appearance is not satisfactory, be badly in need of the development of new surface treatment. In recent years, people trying to develop a variety of new technologies, such as micro arc oxidation technology, the betterOne Micro-arc oxidation mechanismMicro-arc oxidation technology is a new surface treatment technology of green environmental protection, can grow in light metal surface in situ ceramic layer directly. Its technological characteristics, surface treatment, as well as the performance of the since the technology was invented by the favour of people, its mechanism is to light metals such as aluminum, magnesium, titanium and its alloy put in electrolyte aqueous solution as anode, using the method of electrochemical spark discharge spots on the surface of the material, the thermal chemistry, plasma chemistry and electrochemistry, under the joint action of metal oxide ceramic layers of a surface modification technologyTwo research methods and technologyThis topic in the research on magnesium alloy electric wheel hub, higher requirements on the toughness of the alloy, so choose AM60B, melt and initial temperature of 468 ℃, the melting end temperature is 596 ℃, the liquidus temperature range of 165 ℃. The chemical composition as shown in table 1.Because of the magnesium alloy electric wheel hub surface area is larger, general above 0.4 m2, require micro-arc oxidation power supply is bigger, this subject adopts the lanzhou university of technology institute of materials and development of MAO - 300 type nc micro-arc oxidation production device (figure 1) micro-arc oxidation on magnesium alloy wheel casting processing, its similar to ordinary anodic oxidation equipment, including special high-voltage power supply, micro-arc oxidation alkaline solution of electrolytic tank, mixing system, cooling system, workpiece with stainless steel plate for peer electrode.With micro-arc oxidation method in sodium silicate and sodium hydroxide electrolyte fluid system in the preparation of magnesium alloy wheel casting oxide ceramic membrane, the concrete technological process first set oxidation process parameters and the alkaline tank sodium silicate solution, the cleaning after micro-arc oxidation of magnesium alloy wheel casting into cell 15 ~ 20 min, clean with clear water tank 2 ~ 4 min, add hot water in hot water (80 ℃, 10 ~ 15 min), closed, then cool in the cold water tank 2 min, hoisted out drainage, drying, examine the hub. After micro-arc oxidation treatment must be closed by hot water, formed by micro-arc oxidation discharge holes so the distribution of the channel and the surrounding a large number of micro cracks will be closed, prevent oxygen to cause oxidation. After completion of micro-arc oxidation, from after micro-arc oxidation on magnesium alloy wheel casting intercept film sample were analyzed, and to facilitate test analysis, request samples made of circular plate, so the sample interception location choice among wheels, most is shown in figure 2. Using scanning electron microscope analysis of oxide filmFigure 1 MAO - 300 type nc micro-arc oxidation power supplyFigure 2 after micro-arc oxidation magnesium alloy wheel hub casting andinterception of membrane layer analysis sampleThree micro-arc oxidation process parameters on the quality of the film Based on the research of the sample and analysis of micro-arc oxidation technology is, in fact, the substrate magnesium magnesium oxide. Figure 3 for the dimension of samples before and after oxidation appearance schematic simulation, which is suitable for ceramic oxide film a outward growth, namely the increase of size part, b is the depth of the internal oxidation to the matrix, a and b interface for initial sample surface position, h for the total thickness of oxide film.Figure 3 samples dimension changes before and after micro-arc oxidation diagram Larger influence on test has a positive voltage, frequency, duty cycle, current density and oxidation time on the process parameters. Due to the electric casting of magnesium alloy surface area is larger, micro-arc oxidation micro-arc discharge must be formed in the surface can occur after a certain thickness of oxide film, so the formation of the oxide film is needed for the voltage doesn't need much, the current is larger, the oxide film formation and the process of thickening, often accompanied by current and voltage mutation. When the oxide film thickness reaches a certain degree, the need to increase the voltage on both ends of the workpiece, usually at around 150 V in the micro arc discharge between the workpiece and the electrolyte. Increased with the increase of voltage, current, micro-arc density is more and more close, more and more bright, and micro-arc constantly beating, basically, the current and voltage, linear increase about 180 V voltage, the density of micro-arc basically meet the technological requirements, the current growth slowly. When the thickness of oxide film reaches a certain electricityFrom electric casting magnesium alloys is not hard to find in the micro-arc oxidation test result analysis, micro-arc oxidation in the process can be divided into two steps, namely the oxide film formation stage and the stage of micro-arc oxidation film discharge, the formation of oxide film phase as the initial stage, the stage of the supply voltage is small, and after the film to produce micro-arc discharge requires high voltage, for magnesium alloy electric casting the large workpiece with micro-arc oxidation processing surface area is larger, the film for a long time, to a large extent affected the production efficiency.Experimental results also found that the dc power of oxide film faster than pulse power, in the absence of micro arc discharge, oxide film layer is not dense, it can be seenfrom appearance, need again with pulse power supply for micro-arc oxidation discharge, the oxide film become more dense. In order to improve the production efficiency, to meet the needs of industrial production, suggest early low voltage adjustable dc constant voltage power supply are available to set up the initial oxidation film, forming a complete insulation film in place to ensure that the first phase, and the oxide film in the late discharge can use digital pulse type adjustable power supply, it can shorten the artifacts of micro-arc oxidation time.The size of the current density in a certain extent reflects the intensity of micro-arc oxidation, strongly affect the resulting performance of the micro arc oxidation ceramic layer. The duration of oxidation also seriously affects the coating corrosion resistance: oxidation time is too short, although generated mainly the dense layer, but the film is too thin, don't have good corrosion resistance; After oxidation time is too long, at some time, with the increase of time, although the overall film thickness increases, but the increase is a loose layer, layer density and thinning trend, does not favor the coating corrosion resistance, also not economic. The density of micro arc also related with the pulse frequency, when the pulse frequency increases, the density of micro arc also gradually increased. Will have the electric field set up suddenly, can produce micro arc. In the basic process parameters such as electrolyte concentration, duty ratio and pulse number of uncertain, the arc voltage is constant commonly, so when the frequency increases, the sustain micro-arc voltage frequency increases, the micro-arc density will increaseFour micro-arc oxide film layer structure characteristicsAfter micro-arc oxidation of magnesium alloy wheel hub interception by Mef3 large metallurgical microscope observation of the sample, the micro-arc oxide film surface morphology as shown in figure 4. Can be seen from the figure in the wheel hub surface layer is made up of many tiny "small volcanic cone" (figure protuberant part around the holes) in dendritic combination, constitute the mesh structure. "Small volcanic cone" center has a small hole, this is the electrolyte reaction with matrix micro-arc discharge channel, namely when the micro-arc spewed molten oxide channel. In addition, because the current micro area local plasma channel is different that differ by the size of the hole, big hole are also distributed around a large number of micro cracks, the generation of micro cracks often related to the stress that exist in the film. With SSM Analysis Analysis software [6] toanalyze the surface density, including 25 m film for sample, the hole surface area ratio of 18%, that of micro-arc oxidation film density is better.Figure 4 magnesium alloy wheel hub micro-arc oxide film layer surface morphologyFigure 5 AM60B magnesium alloy micro-arc oxidation film section morphology by SEM Figure 5 is through JMS - 6700 - f field emission scanning electron microscopy (sem) observed the micro-arc oxide film layer section morphology photos. Figure 5 shows the average film thickness of about 22 (including m, the oxide film and substrate with good, decomposition of a distinct, density on the interface is good, no big holes. By figure 5 can also see, micro-arc oxide film by the outermost layer of loose layer, the inside of the transition layer and layer in between density of three parts, the transitional layer is the interface film layer and substrate, holes and other defects existing in the loose layer, dense layer is the key to improve its corrosion resistance.Figure 6 is obtained by Phlip X 'pert X-ray diffractometer AM60B magnesium alloy wheel hub of micro-arc oxidation film XRD spectrum, according to the intensity of diffraction peak accumulation analysis shows that the matrix of Mg peak relatively obvious, the main phase of micro-arc oxidation coating is cubic structure of MgO style, surface with Mg2Si2O4 and MgAl2O4 spinel phase, according to the test conditions that may also contain SiO2, MgF2 and small amounts of Mg (OH) 2, and the oxide of Al, K and Na. Studies have shown that MgAl2O4 and Mg2Si2O4 can improve the wear resistance of ceramic layer and MgO style the corrosion resistance of ceramic layer play a very important role. This is the micro-arc oxide film performance is higher than the root cause of the anode oxidation membrane performance. In addition, micro-arc oxidation ceramic layers of low porosity, and to improve the corrosion resistance of the coatings; Ceramic layer from the substrate on the growth, combined with matrix closely, therefore, is not easy to fall off. In addition, the technology can generate uniform film both inside and outside the material surface layer, expand the scope of application of micro-arc oxidation.Figure 6 AM60B magnesium alloy micro-arc oxidation film XRD spectrumFive To detect the corrosion resistance of the micro-arc oxide film layer In order to meet the requirements of the use of electric cars, micro-arc oxidation on magnesium alloy electric wheel hub on the corrosion resistance test, salt spray testing machine mainly USES the WJ - 90 after micro-arc oxidation treatment of the surface of the wheel hub for salt spray test. After testing found that did not use hot water seal processing of the surface of the wheel hub 48 h corrosion rate was 0.108%, while only 0.073%, afterhot water hole sealing hubs such as chromium than other chemical surface treatment processing of low corrosion rate (0.6%). [9], that magnesium alloy after micro-arc oxidation electric wheel hub surface corrosion resistance is superior. To evaluate a rough check the appearance of the film, feel is very good, membrane layer uniform light show that membrane surface appearance level is higher. Practice shows that without the micro-arc oxidation of the surface of the magnesium alloy wheel casting coating, its poor corrosion resistance, abrasion resistance, in a very short period of time, began to appear on the surface of parts oxidation falls off phenomenon, it is difficult to sell in the market; After micro-arc oxidation treatment, its corrosion resistance, wear-resisting performance is significantSix The conclusion(1) quality of micro-arc oxidation on magnesium alloy electric wheel hub surface influence factor has a positive voltage, frequency, duty cycle, current density and oxidation time on the process parameters. Optimum process parameters for 150 ~ 180 V voltage, current density of 1.1 A/dm2, oxidation time to 20 min, 400 Hz frequency, duty cycle of 20%.(2) the oxide film is divided into two layers of loose layer and dense layer structure, the dense layer is the main body, the film formed by cubic structure of MgO style, the surface is MgO style and MgA12O4, spinel phase mixture, and combined with matrix and closely for hard ceramic layer and played a key role of the magnesium alloy surface anticorrosion(3) the micro-arc oxidation technology for new surface treatment technology of environmental protection, but its large area needed for the magnesium alloy casting film for a long time, the production efficiency is low, the mass production to meet the large area of magnesium alloy castings, micro-arc oxidation power supply can be established by using dc power first initial oxidation film layer, then use pulse power arc discharge strengthening oxide film layer, the ways which are already so dense and hard ceramic oxide film layer can be obtained, also can greatly improve production efficiency.镁合金电动车轮毂微弧氧化生产研究国内外大多数电动车车辆配置为铝合金轮毂，其在质量、节能、减震、降噪和车辆动力学特性等指标大大低于镁合金。