Study On Preparation Of Mg-Li-Al And Mg-Li-Al Based Alloys By Electrolysis In Molten Salt

Mg-Li-Al based alloy is one of the most representative light alloys, which is widely used in aviation, aerospace and electronic industries as an ideal structure material. At present, good quality Mg-Li-Al or Mg-Li-Al based alloys, like LA141, usually is obtained by metal casting. However, this method has many flaws or disadvantages. Preparation of Mg-Li-Al based alloy by electrolysis in molten salt is a novel technique and method, which had many advantages, like controllability of alloy features, simplicity of production equipment and processes and being easy for mass production. Because of these advantages, this preparation method has attracted much attention in recent years.In this paper, we have studied preparation of Mg-Li-Al, Mg-Li-Al-Sm and Mg-Li-Al-La alloy by direct electrochemical reduction in molten salt. The preparation process and electrochemical mechanism have been deeply investigated.In the first section of this thesis, Mg-Li-Al alloys were prepared by co-electrodeposition using graphite as anode and molybdenum as cathode in molten LiCl-KCl-MgCl2-AlCl3-KF system. Alloy composition could be controlled by technological parameter of electrolysis. Take the components and current efficiency into consideration, we obtained a better electrolytic process parameters:electrolysis time,60 min; current density,2.5A/cm2; electrolysis temperature, 630℃.In the second section of this thesis, Mg-Li-Al-Sm alloys were prepared by electrolysis using inert cathode and active anode in molten KCl-LiCl-MgCl2-KF-Sm2O3 system. Electrolytic behaviours and process of these key ions'electrochemical deposition have been investigated. We found a preparation parameter for high samariumcontent in alloys:current density,15.5 A/cm2; electrolysis temperature,580℃; electrolysis time:2h.In the third section of this thesis, Mg-Li-Al-La alloys were prepared by electrolysis using inert cathode and active anode, and La2O3 as raw material in molten KCl-LiCl-MgCl2-KF-Sm2O3 system. We have investigated electrolytic behaviours of La on different inert cathodes and found a better parameter for preparation of Mg-Li-Al-La alloys by galvanostat electrolysis:current density,12.4 A/cm2; electrolysis temperature,580℃.