The Preparation And Study On Magnesium-Strontium-Calciumin Molten Salt Electrolysis Method

Improving the magnesium alloy high-temperature property of is the important issues in the last 30 year, the scholars pay a lot of attention about the study of heat-resistant magnesium alloy, and have do a lot of work.Mg-Sr-X alloys have good heat-resistance. Mg-Sr-X alloys and its preparing technology is current research interest of heat-resistant magnesium alloys. The key research of the paper is that the major theoretical and technological issues of the Mg-Sr-Ca alloy prepared by electrochemical reduction, and owning new Mg-Sr-X alloys and new prepare methods.In this paper, according the conventional theory of molten salt electrolysis, we designed the prepared process of the Mg-Sr-Ca alloy's electrochemical reduction. We calculated and analysised the decomposition voltage molten salt and the electrode potential the metals. We designed the electrochemical reduction experimental device, and on it we do a series of experimental studies of Mg-Sr-Ca alloy electrochemical reduction. And used optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and other inspect means to analyse the experimental results. The results show that:â‘ Most of molten salt's density is higher than most of melting magnesium-alloy density, the majority of molten salt in melting magnesium-alloy will sink, only a small number of lithium salts and its salt mixture can be suspended on some melting magnesium-alloy.â‘¡SrCl₂-CaCl₂ mixed molten salt system has good electrolytic properties, is the ideal electrolyte. SrCl₂-CaCl₂ mixed molten salt's density is higher than the density of Mg-Al alloy melt density, when electrolysis, SrCl₂-CaCl₂ molten salt mixture under the Mg-Al alloy melt. At the same time, doing the design and collocate of molten salt, must consider the density difference between molten salt and alloy melt can be separated.â‘¢When the melting magnesium-alloy placed on the molten salt, the electrolysis devices should be to prevent Mg and the alloy elements burning and oxidation, and eliminate the gas generated in the electrolysis, and the adjustment of electrode and the current parameters. Etc.â‘£In the electrolytic process of SrCl₂-CaCl₂ molten salt mixture, will simultaneity eliminate Sr and Ca. Of these, the density of Sr is larger than Mg-Al alloy melt density, will be sinking to SrCl₂-CaCl₂ mixed molten salt and lead poisoning. Controling electrolytic cathode current density and temperature in appropriate areas, can impeove the spread and the yield of Sr. The density of Ca less than the density of Mg-Al alloy melt density, is conducive to the spread of Ca, at the same time, the liquating of Ca and the burning of Ca will influence the yield of Ca.⑤In the Mg-Sr-X alloy microstructure prepared by the electrochemical reduction, Sr, Ca alloying elements gathered in the dendrite / boundary of the primary phaseα-Mg. The rod-shaped phase in the boundary is very similar to Al4Sr phase of Mg-4Al-2Sr alloy, and the spectrum analysis showed that these peculiar phases are Al4Sr and Al2Ca. These high melting point of the hard phase, can effectively pinning the grain boundary to raise the magnesium alloy mechanical properties. When Sr, Ca content is very low, Al₄Sr, Al₂Ca will reduce and still have Mg₁₇Al₁₂.