| Al-Mg alloys are an excellent lightweight metallic material due to their attractive properties, such as low density, high volumetric heat content, high specific strength and stiffness, strong corrosion resistance. Al-Mg alloys also play an important role in the high energy physics research areas. In the scientific research of Z-pinch-driven inertial confinement fusion(ICF), the wire array load in common use is the ultrafine tungsten wire arrays, whose diameter are less than 10 microns. These tungsten wire arrays can ensure a high power X-ray emission and yield. However, in order to meet the requirements of Z-pinch-driven ICF, the X-ray transmission power and yield still need to increase substantially. Covering a coating film of Al-Mg alloys onto the ultrafine tungsten wire arrays may gain better X-ray benefits.In this thesis, the electrodeposition system is the low temperature inorganic molten salt AlCl3-NaCl-KCl-MgCl2 system. Preliminary studies of the Al-Mg alloys coating film prepared by electrodeposition perform on the copper substrate firstly. Then we carry out the research of coating preparation on the tungsten substrate and ultrafine tungsten wire. Finally we explore the feasibility of the preparation of Al-Mg coating film by using choline chloride –urea ionic liquid system.The factors which may affect the morphology of Al-Mg alloys coating layers and the Mg content in the deposition are investigated, such as electrolysis potential, electrolysis time, electrolysis temperature and the MgCl2 concentration. Theoptimized electrolysis process of the Al-Mg alloys coating film on copper substrateis determined as follows: electrolyte composition: AlCl3:NaCl:KCl=78:11:11(wt%),mass fraction of MgCl2: 2.5%~4%, electrolysis potential: 1.22~1.35 V, electrolysistemperature: 200~220℃, electrolysis time:20~45min. The Mg atom content can beas high as 9.55%.The results of the coating electrodeposited on tungsten substrate show that when the atom content of Mg in the coating is low, the coating is made up of solid solutions(α-phase).With the increasing of the Mg content, the amorphous state α-phase grows gradually, and the corrosion resistant of the coating becomes better. When the Mg content reaches a certain constant, the crystalline state intermeatallic compound Mg2Al3(β-phase) precipitates, which disperses in the α-phase. With the increasing of Mg content in the alloy coating, the β-phase grows more and more, which results in reducing of the coating’s corrosion resistant.The Mg content is proportional to escalated potential when the potential ranges from 1.22 V to 1.3V, which results in a growth of α-phase and a decrease of the grain size. At the potential of 1.3V, the atom content of Mg in the coating is 12.93% and it declines when potential is beyond 1.3V, also the grain size becomes larger. The thickness of Al-Mg coating is proportional to escalated potential. With the increasing of the mass fraction of MgCl2 in the molten salt, the Mg content of the coating increases and the β-phase grows more and more. The Mg atom content can be as high as 16.12% when the mass fraction of MgCl2 is 4%.The optimized electrolysis process of the Al-Mg alloy coating film on the surface of ultrafine tungsten wire is determined as follows: electrolysis temperature: 220℃, electrolysis prtential: 1.3V, electrolysis time: 30 min, mass fraction of MgCl2: 3.5% to 4%. The Mg atom content can be as high as 14.98%.Electrochemical studies indicate that in low temperature molten salt AlCl3-NaCl-KCl-MgCl2 system, some irreversibility is involved in the deposition of Al-Mg alloys on tungsten electrode. The nucleation mechanism of the Al-Mg alloys is similar to Al deposition in inorganic molten salts.The codeposition potential of Al-Mg alloys coating in the choline chloride–urea ionic liquid system is-1.0V. After 60 minutes constant potential electroposition at 80℃, we can get a thin coating layer on the surface of the copper electrode, where the atomic rate of Al and Mg is nearly 4:1. The invertibility of Al-Mg alloy in the deposition on copper electrode is poor. |
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