Preparation of Mg-Li-Al-Zn Master Alloy in Air by Electrolytic Diffusing Method

摘要

Electrolytic diffusing method was conducted at 500 deg C to prepare Mg-Li-Al-Zn master alloy in air. It was also explored for the melting and casting of Mg-Li alloy in air, as the Mg-Li-Al-Zn master alloy used as raw material. A mixture of 45 mass percent lithium chloride (LiCl) and 55 mass percent potassium chloride (KC1) was employed as the electrolyte. Mg-9 mass percent Al-l mass percent Zn (AZ91) alloy was used as cathode material while graphite selected as anode. Experimental results showed that the electrolysis current linearly depended on the applied working voltage. Deposition of lithium occurred on the cathode surface. After the electrolysis experiments, Mg-12mass percent Li-9mass percent Al-1 mass percent Zn alloy sheet can be obtained. At working voltage of 4.2V and one hour electrolysis, the hexagonal-closed-pack AZ9ID sheet (1.5-mm thickness) was fully converted to body-centered-cubic Mg-Li-Al-Zn alloy. The formation of Mg-Li phase during electrolysis was studied by inductively coupled plasma-atomic emission spectrometer (TCP), X-ray diffraction, and optical microscopy. It is diffusion rather than deposition rate (electrolysis current) that controlled the depth of Mg-Li phase formed in the cathode sample. The Mg-Li-Al-Zn alloy used as master alloys could be melted and casted in air without ignition. However, the content of lithium in the as-cast block was reduced to 3.77 mass percent, properly due to oxidation of lithium metal during melting.