The Process And Mechanism Of Cu-Mg Master Alloy Prepared By Molten Salt Electrolysis

Cu-Mg is a typical high strength and high conductivity alloy,which have been widely used in the field of electronic communication,transportation and so on.In this paper,MgO was taken as raw material,LiF-MgF₂-BaF₂-KCl as electrolyte,copper rods as cathode,Cu-Mg alloy was prepared by molten salt electrolytic method.The physical and chemical properties of the molten salt system,electrolytic process had been studied systematically.The composition and morphology of the alloy had analyzed by XRD and SEM detection methods.At the same time,the electrochemical behavior of Mg in the system was explored by means of cyclic voltammetry and chronoamperometry.Research results of physical and chemical properties of molten salt system showed that with the increase of temperature,the electrical conductivity of molten salts increased gradually,the density was linear decrease.When the temperature was low,viscosity reduced significantly with the decreaseof temperature,further increase in temperature,reduce of viscosity became smooth.With the increase of MgO,conductivity and density of the system first increased and then decreased,when the temperature of 1233 K and the MgO content was1.5wt%,the conductivity and density reached the maximum value;viscosity with MgO content increased first decreased and then increased,the system with high MgO content on the viscosity of molten salt had great influence.Under the same temperature and MgO content,the performance of LiF-MgF₂-BaF₂-KClMgO molten salt system was better than that of LiF-MgF₂-BaF₂-MgO molten salt system.Adding proper amount of KCl in the electrolyte system can improve the conductivity of molten salt,increase the density of molten salt and reduce the viscosity of molten salt.For the electrochemical mechanism of LiF-MgF₂-BaF₂-KCl-MgO molten salt system,the results showed that electrochemical magnesium ion in tungsten electrode reduction step was 2 electron transfer process,the electrode reaction was: Mg²⁺+2e→Mg.The deposition process of magnesium in the tungsten cathode was a quasi reversible controlled by diffusion.At 1233 K,the diffusion coefficient of Mg²⁺ in molten salts was 1.28×10^-5cm2·s^-1.For the preparation of electrolytic process of Cu-Mg alloy research,the results showed that the cell voltage was increased with temperature,increased with the increase of cathodic current density,and the electrolysis time extents,cell voltage increased.In a certain temperature range,the electrolytic temperature increased by 30 degrees Celsius,the tank voltage decreased by 0.1V;the cathode current density increased from 0.8A·cm^-2 to1.4A·cm^-2,and the tank voltage was increased by about 0.3V.The electrolysis temperature andcathode current density increased,both of which would make the current efficiency first increased and then decreased,when the electrolysis temperature was 1233 K,the cathode current density was 1.2A·cm^-2,the current efficiency reached highest about 81.2%.The polarization principle estimate electrolytic process of back EMF,it was concluded that the molten salt system in 1233 K for electrolysis,the anti electromotive forced for 2.45 V.For the characterization of Cu-Mg alloy,XRD analysis results showed that the diffraction peak of the alloy can be accurately matched with the standard card of MgCu₂,explaining that copper and magnesium intermediate compound was MgCu₂,no elemental Mg diffraction peak in the XRD graph,Mg all existed in the alloy in the form of MgCu₂ compound.SEM analysis results showed that the MgCu₂ crystal phase was mainly distributed in the Cu matrix,and the Cu based crystal phase was uniformly distributed with a small granular MgCu₂ crystal.