脉冲电沉积制备铝及铝镁合金的研究

发布时间：2018-03-06 09:48

本文选题：铝　切入点：铝镁合金　出处：《沈阳大学》2016年硕士论文　论文类型：学位论文

【摘要】：铝及铝镁合金具有优异的耐蚀性、装饰性、抗氧化性和良好的力学性能成为理想的构件防护材料,由于铝镁合金的质量轻,理论储氢量高,作为储氢材料具有广泛应用前景。为使铝镁合金得到良好的应用,需要制备超细结构纯净合金,电沉积是制备高纯合金的有效方法之一。利用电沉积法可在非水液体中电化学沉积出金属铝及铝镁合金,获得高纯度的镀层。在电沉积铝及铝镁的实验中,沉积体系的选择是制备镀层的基础,沉积方法的选择是制备镀层的关键,通过控制沉积参数实现对合金微观组织结构和成分的控制,可制备高纯超细合金。AlCl_3-LiAlH_4有机溶剂体系是最早应用于电解铝的体系,可在室温条件下进行,不仅有效的节约能源,还不影响基体的力学性能。本文在国内外电沉积铝及铝镁合金的研究基础上,在AlCl_3-LiAlH_4-苯-THF有机溶剂体系中通过直流和脉冲两种方式电沉积制备铝及铝镁合金。采用三电极体系进行电化学实验,通过交流阻抗法(EIS)研究了制备铝镁合金的电解液的导电性,并利用交流阻抗法和Tafel极化曲线研究了铝及铝镁合金镀层的耐腐蚀性能。通过扫描电镜(SEM)、能谱(EDS)以及X射线衍射(XRD)检测和分析铝及铝镁合金的镀层形貌、成分及含量。通过电沉积法制备铝及铝镁合金镀层,研究了电流密度、通断比、频率、镁离子引入方式及实验环境和条件等对铝及铝镁合金组成、形貌和晶体结构等的影响。结果表明,利用脉冲电沉积可以制备出高纯度铝镀层,镀层中铝的含量高达99.43wt%,改变通断比、电流密度等参数对电沉积铝镀层有较大影响,通断比越小,镀层中晶粒尺寸越小,最小晶粒可达0.5mm,在一定范围内晶粒尺寸随电流密度的增大而增大,少量添加MgCl_2可以细化晶粒。利用镁条作阳极,电解液中添加MgCl_2进行直流电沉积制备铝镁合金镀层时,通过XRD谱图可以看出铝镁合金镀层的主要成分为Al_3Mg_2和Al_12Mg_17。当电流密度为0.3A/cm2时,铝镁合金中镁含量为4.61wt%,在一定范围内,电流密度越大,铝镁合金中镁含量越高。增加镁条数量,铝镁合金中的镁含量有所增长,但增长的趋势不大,镁条数量为5条时,铝镁合金中镁含量为7.56wt%。脉冲电沉积铝镁合金镀层时,镀层的晶粒尺寸和镁含量随电流密度的增加而增加,当电流密度为20mA/cm2,晶粒尺寸可达30-50mm,铝镁合金中的镁含量为3.17wt%。通断比越大,镀层的晶粒尺寸越大,镀层中镁含量越高,通断比为0.02:0.08时,晶粒尺寸最小可达5mm。通过交流阻抗法和极化曲线法对镀层进行耐腐蚀实验,当检测铝镀层的耐腐蚀性时发现,通断比越大,阻抗越大,耐蚀性越好,即晶粒尺寸越大,耐蚀性越好。对铝镁合金镀层进行耐腐蚀实验时发现,在研究范围内(研究所选镁含量范围写上),当镁含量为2.54%(质量分数)时,阻抗最大,即铝镁合金中镁含量越高,阻抗值越大,镀层的耐腐蚀性能越好。
[Abstract]:Aluminum and aluminum-magnesium alloys have excellent corrosion resistance, decoration, oxidation resistance and good mechanical properties. In order to make the aluminum magnesium alloy get good application, it is necessary to prepare pure superfine structure alloy. Electrodeposition is one of the effective methods for preparing high purity alloys. High purity coatings can be obtained by electrodeposition of aluminum and aluminum-magnesium alloys in non-aqueous liquids. The selection of deposition system is the basis of coating preparation, and the selection of deposition method is the key to the preparation of coating. The microstructure and composition of alloy can be controlled by controlling deposition parameters. The organic solvent system of high-purity superfine alloy. ALCL _ 3-LiAlH _ S _ 4 is the first system used in electrolytic aluminum, which can be carried out at room temperature, which not only saves energy, but also saves energy effectively. In this paper, based on the research of electrodeposition of aluminum and aluminum-magnesium alloy at home and abroad, Aluminum and aluminum-magnesium alloys were electrodeposited in AlCl3-LiAlH4benzen-THF organic solvent system by direct current and pulse deposition. Electrochemical experiments were carried out in a three-electrode system, and the conductivity of the electrolyte prepared by AC-EIS was studied. The corrosion resistance of aluminum and aluminum-magnesium alloy coatings was studied by means of AC impedance method and Tafel polarization curve. The morphology of aluminum and aluminum-magnesium alloy coatings was detected and analyzed by SEM, EDS and X-ray diffraction (XRD). Composition and content. Aluminum and aluminum-magnesium alloy coatings were prepared by electrodeposition. The current density, on-break ratio, frequency, mg ~ (2 +) introduction mode, experimental environment and conditions were studied. The results show that the high purity aluminum coating can be prepared by pulse electrodeposition. The aluminum content in the coating is up to 99.43 wt.The parameters such as current density have great influence on the electrodeposition of aluminum coating. The smaller the on-break ratio is, the smaller the grain size in the coating is, and the minimum grain size can reach 0.5 mm. In a certain range, the grain size increases with the increase of current density. A small amount of MgCl_2 can refine the grain. When adding MgCl_2 to the electrolyte to prepare Al-mg alloy coating, the main composition of Al-Mg alloy coating is Al_3Mg_2 and AlSI-12Mg17.When the current density is 0.3A / cm ~ 2, the magnesium content in Al-mg alloy is 4.61wtcm ~ 2, and the content of mg in Al-mg alloy is 4.61wtcm ~ 2, which is within a certain range. The higher the current density, the higher the content of magnesium in Al-Mg alloy. When the number of magnesium bars is increased, the content of magnesium in Al-Mg alloy will increase, but the trend of increase is not obvious, when the number of magnesium bars is 5, The grain size and magnesium content of aluminum-magnesium alloy coating increase with the increase of current density. When the current density is 20 Ma / cm ~ 2, the grain size can reach 30-50 mm, and the magnesium content in aluminum magnesium alloy is 3.17 wt.The ratio of open to break increases. The larger the grain size of the coating is, the higher the content of magnesium in the coating is. The ratio of open to break is 0.02: 0.08, and the minimum grain size can be up to 5 mm. the corrosion resistance of the coating is tested by means of AC impedance method and polarization curve method. When the corrosion resistance of aluminum coating is tested, it is found that, The larger the ratio of open to break, the greater the impedance, the better the corrosion resistance, that is, the larger the grain size, the better the corrosion resistance. In the scope of study, when the content of magnesium is 2.54 (mass fraction), the impedance is maximum, that is, the higher the content of magnesium, the greater the impedance, and the better the corrosion resistance of the coating.
【学位授予单位】：沈阳大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ153

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