Study On Process And Mechanism Of Al-Sr Alloy Prepared By Molten Salt Electrolysis

Al-Sr master alloy was a kind of new high-performance modifier developed in recent years,which could change morphology of silicon phase in aluminiumsilicon alloy series and improve alloy performance and mechanical performance（such as ductility and abrasion resistance property）at heat treatment condition.Compared with the traditional sodium salts modifier,Al-Sr master alloys have many advantages,such as effective time modificated,without over modificated behavior,remelted availability,the high yield,volatile little,low equipment corrosion and so on,so they were studied and promoted at home and abroad.Now the preparation of Al-Sr aluminum alloys doped gradually abandon the mixing method,but mainly by molten salt electrolysis.And there are many cases to achieve the preparation of Al-Sr alloys by the molten salt electrolysis.However,only few study of the electrochemical reduction process of strontium ions on the cathode was carried out.Therefore,in the LiF-SrF₂-SrO molten salt system,the physical chemical properties of molten salt was studied,then Al-Sr master alloy was prepared by molten salt electrolysis method with the sunken liquid cathode,further,strontium electrolytic deposition conditions and its influencing factors was analyzed,and alloy products were characterized.Based on the above,the electrochemical behavior of strontium ion in the cathode and control procedures was conducted.The main conclusions can be summarized as follows:（1）The effect of the addition of SrO on physical and chemical properties of LiF-SrF₂ molten salt system was studied in this paper.The molten salt conductivity and density increased firstly and then decreased with the increasing of SrO,the molten salt conductivity and density increased firstly and then decreased with the increasing of SrO,both molten salt conductivity and density increase and then decrease,and reached maximum at 2wt% SrO;viscosity increased with the increasing of SrO,while surface tension wasn’t influenced obviously.The research indicated that with the increase of temperature,the electrical conductivity increase,and the viscosity,density and surface tension decrease.（2）In the LiF-SrF₂-SrO molten salt system,the electrochemical reduction process of Sr²⁺ on tungsten electrode was a process in which two electrons was transferred in a step,and the electrode reaction is Sr²⁺+2e^-→Sr.The research indicated that the cathode process of Sr²⁺ on tungsten electrode was a quasi-reversible reactionand controlled by the diffusion step of ions.The diffusion coefficient was 3.71×10^-5cm²·s^-1.（3）According to results of the electrochemical analysis,the liquid aluminum works as cathode,the Al-Sr master alloy was prepared in LiF-SrF₂-SrO molten salt system,and the optimum process parameters were obtained.The X-ray diffraction and scanning electron microscope analysis were carried out,and the results show that it is feasible the preparation of Al-Sr master alloy by molten salt electrolysis method with the sunken liquid cathode.