工艺参数对电沉积制备铝镁合金的影响

目的以AlCl_3和LiAlH_4为溶质,苯和四氢呋喃为溶剂,进行电沉积铝镁合金,探索制备铝镁合金的最佳工艺条件。方法在AlCl_3-LiAlH_4-苯-四氢呋喃体系中,采用镁作阳极,通过预电沉积获得一定浓度的Mg~(2+),从而进行电沉积制备铝镁合金镀层。改变电流密度、沉积时间、预电沉积时间和预电沉积次数等参数,以探究工艺参数对铝镁镀层的形貌、晶粒大小和镁含量的影响,并通过SEM和EDS检测和分析铝镁合金的镀层形貌、成分及含量。结果镀层主要成分为Al_3Mg_2和Al_(12)Mg_(17),当电流密度为16.67 m A/cm~2时,获得的镀层表面效果最好,其晶粒尺寸可达1~2mm。预电沉积次数越多,通过预电沉积获得的Mg~(2+)越多,铝镁合金镀层中镁的含量越高,最高可达2.93%(质量分数)。结论在一定范围内,镀层中的镁含量随预电沉积时间的增加而提高。预电沉积次数越多,通过预电沉积溶解的Mg~(2+)越多,铝镁合金镀层中的镁含量越高。当沉积时间过长时,不利于镀层中镁含量的提高。铝镁镀层中的镁含量越高,电化学阻抗越大,腐蚀电位越大,镀层的耐腐蚀性能越好。

Effects of Technological Parameters on Aluminum-magnesium Alloys Prepared by Electrodeposition

The work aims to explore best technological parameters of preparing aluminum-magnesium alloy by electrodeposition with AlCl3 and LiAlH4 as solutes, and benzene and tetrahydrofuran as solvents. Mg ions (Mg2+) of certain concentration were obtained by pre-electrodeposition using a pure Mg anode in AlCl3-LiAlH4-benzene-tetrahydrofuran (THF) system, so as to prepare aluminum-magnesium alloy coating by electrodeposition. Effects of technological parameters on morphology, grain size and magnesium content were investigated by changing parameters including current density, electrodeposition time, pre-electrodeposition time and times. Coating morphology, composition and content were tested and analyzed by using scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Principal components of the coating were Al3Mg2 and Al12Mg17. The surface state was the best and grain size was about 1~2 mm provided with current density of 16.67 mA/cm2. The more the pre-electrodeposition times were, the more Mg2+ were obtained by pre-electrodeposition, and the higher the magnesium content (of which mass fraction might be up to 2.93%) was. Magnesium content of the coatings increases as the pre-deposition time increases in a certain range. The higher the pre-electrodeposition frequency is, the more dissolved Mg2+ ions are, the higher magnesium content of aluminum-magnesium alloy coatings is. Improvement of magnesium content of the coatings will be inhibited if electrodeposition time is too long. The magnesium content is in direct proportion to electrochemical impedance, corrosion potential and corrosion resistance of the coatings.