Preparation process of magnesium alloys by complex salt dehydration-electrochemical codeposition

ABSTRACT

High-purity anhydrous MgCl₂-containing molten salt was directly synthesized from MgCl₂ · 6H₂O via complex salts dehydration and protection. After that, Mg-Al and Mg-Zn alloys were prepared by electrochemical codeposition. The hydrolysis processes of magnesium chloride hexahydrate in various chloride mixtures were studied. Then, the preparation process was studied and the dehydration mechanism was put forward. NH₄Cl·MgCl₂·nH₂O formed under 300°C inhibits the formation of hydrolysate during the dehydration process. KMgCl₃ and K₃NaMgCl₆ formed above 400°C can further protect the unstable anhydrous MgCl₂. Therefore, high-purity anhydrous MgCl₂-containing molten salt with w(MgO)/w(MgCl₂) being 0.016 wt.% was obtained. The current efficiency was above 81% and 97%, respectively, when preparing Mg-Al alloys and Mg-Zn alloys, and the alloying elements were distributed homogeneously in the alloy matrix.

KEYWORDS:

• magnesium alloys
• dehydration
• hydrolysis
• electrochemical

Highlights

1. The preparation process of magnesium alloys from MgCl₂·6H₂O was studied.

2. The hydrolysis process of MgCl₂·6H₂O in different systems was investigated.

3. Various Mg-Al and Mg-Zn alloys were prepared by electrochemical codeposition.

4. High-purity electrolyte was prepared by complex dehydration and protection.

Additional information

Funding

This project was supported by the National Natural Science Foundation of China under Grant 51501178; Open Research Fund of State Key Laboratory of Multiphase Complex Systems under Grant MPCS-2017-D-09; and Fund of State Key Laboratory of Multiphase Complex Systems under Grant MPCS-2017-A-05.