Study On Preparation Of Mg-Sm Alloys By Molten Salt Electrolysis

Since Magnesium alloys has reduced the weight of structure,fuel consumption and improved the mobility,it is widely applied in automotive,defense,aerospace and other fields.The content of Rare earth element in the magnesium matrix solid solubility is high,which can significantly improve the strength,corrosion resistance and creep resistance of magnesium alloys.Compared with La,Ce,Pr,Nd and other magnesium-rare earth alloys,Mg-Sm alloys has the better strengthening effect with low content of samarium.As we all know the molten salt electrolysis has the characteristics of simple process,uniform alloys composition,low energy consumption and low impurity content of oxide compared with the traditional mixed.Therefore,this paper make some researches and analysis on preparation of Mg-Sm alloys by molten salt electrolysis.Firstly,cyclic voltammetry and square-wave voltammetry was used to research the electrochemical behavior of molybdenum and magnesium electrode in NaCl-KCl-SmCl3 system.Secondly,the effect of SmCl3 content,temperature and time on the dissolution loss was studied in NaCl-KCl-SmCl3 system.Finally we prepared Mg-Sm alloys by constant current electrolysis method using graphite as the anode,magnesium as the cathode,alumina crucibles as electrolysis.The effect of cerium content,cathode current density and electrolysis temperature on the current efficiency was studied in NaCl-KCl-SmCl3 system and obtained optimum synthesis conditions of Mg-Sm alloys.ICP,XRD,SEM were used to analyses samarium content of magnesium samarium alloys and the morphology of magnesium samarium alloys.The results showed that there was an electron transfer reaction on the molybdenum electrode surface at 730? in NaCl-KCl-SmCl3 system and the electrochemical step Sm(?)/Sm(0)was not observed within the electrochemical window.The reaction is Sm(III)/Sm(II)reversible oxidation-reduction reaction.In the under potential deposition process,xMg+Sm(II)+2e?MgxSm was occurred on the magnesium electrode surface.The Mg-Sm alloys were characterized by X-ray diffraction and theXRD results showed that the MgxSm compound was Mg41Sm5 alloys.The dissolution loss of metal Sm in NaCl-KCl-SmCl3 molten salt system contains both physical dissolve and chemical dissolve.After 90 minutes,the dissolution reached to balance in the molten salt system.The dissolution loss will be enhanced with the temperature,dissolved time and SmCl3 content.According to the impact importance extent,time,the content of SmC13,temperature impact the dissolution loss.The effect of current density,electrolysis time,temperature and SmCl3 content on the current efficiency was studied in NaCl-KCl-SmCl3 system preparing Mg-Sm alloys through galvanostatical electrolysis.Results showed that current efficiency increased firstly and decreased subsequently.Samarium content of magnesium samarium alloys increased firstly and decreased subsequently when current efficiency,SmCl3 content and temperature is increasing.And samarium conten increased with the electrolysis time increasing.To get the optimum results,Mg-Sm alloys was obtained by galvanostatical electrolysis on Mg electrodes.The best experimental condition is that the temperature is 750?,the current density is 1 A/cm2,the content of SmCl3 is 25 wt%and the electrolysis time is 1 h.Under these conditions the current efficiency is up to 41.3%and the content of samarium is 24.6 wt%of as-obtained Mg-Sm alloys.The XRD,SEM show that the elements of Sm exist as Mg41Sm5 phase in the alloys.and in the region of the rich magnesium the elements of Sm exists as solid solution.