| Adding an appropriate amount of Y to the Al-Cu series alloy can not only improve the high temperature performance and strength,but also improve its corrosion resistance,making up for the deficiency of the Al-Cu series alloy.Among the methods of mixed melting,thermal reduction and molten salt electrolysis plus Y,the molten salt electrolysis method has more advantages.The experimental research object of this thesis is the fluoride-oxide molten salt system（Na3AlF6-AlF3-LiF-Y2O3）,which uses the isothermal saturation method and the Hitov method for the rare earth oxide Y2O3 in the Na3AlF6-AlF3-LiF fluoride salt system.The dissolution behavior and ion migration mechanism are studied.The dissolution equilibrium time of Y2O3 in AlF3-（Li,Na）F melting system in the range of 995℃1115℃is not less than 40min.The solubility of Y2O3 increases with the increase of the system temperature and the NaF/AlF3 molar ratio,and the dissolution of Y2O3 in the NaF-AlF3-LiF（5wt%）system in the temperature range of 995℃1115℃is mainly chemical dissolution..Temperature has little effect on the solubility of Y2O3,and NaF/AlF3（molar ratio）plays a major role.When the NaF/AlF3 molar ratio is higher than 2.3,the dissolution of Y2O3 in the system tends to be stable,and below 2.3,it quickly decreases small.At the same time,at a temperature of 995℃1115℃,NaF/AlF3（molar ratio）2.32.9and LiF（wt%）added amount of 3%9%,the solubility（S）and temperature（T）,NaF/A regression equation between the three factors of AlF3 molar ratio（M）and LiF（wt%）addition（W）.When the temperature is fixed,the amount of LiF added gradually increases,enhancing the conductivity of the molten salt and the solubility of Y2O3 continues to increase.In the study of ion migration number,first by studying the thermodynamic basis of Y2O3in the Na3AlF6-AlF3-LiF melt,it is clear that Y2O3 has two forms of physical and chemical dissolution.At the same time,it was found that under constant current conditions,the ions containing Y element dominate the transport process and change with temperature,molar ratio,and current density.As the temperature increases,the current density increases,the NaF/AlF3 molar ratio increases,and the number of Y ion migration also increases.In order to study the electric field distribution in the electromigration tank,based on the experimental tank size,the mathematical and physical model of the two-way flow field-electric field coupling was established based on the physics coupling function of COMSOL,and the internal electric field distribution was simulated by the ANSYS calculation platform And verify the reliability of the model and boundary conditions and related parameters.The anode of the electric field of the rare earth electrolysis cell is connected to the positive electrode of the power supply,and the cathode is connected to the negative electrode of the power supply,and the current density of the anode is greater than that of the cathode.The electrolytic cell adopts a plug-in structure.Under the premise that the electrolyte conductivity in the electrolytic cell is regarded as an isoelectric conductivity region,the electric potential in the electrolytic cell is evenly distributed and the equipotential line between the Yin and Yang poles will be perpendicular to the ground.The bottom of the electromigration solution tank does not change much due to the absence of gas.The flow field changes are mainly concentrated in two small areas,one is between the cathode and the anode on the surface of the molten pool,and the other is a tiny area at the bottom of the anode.The main reason for the high flow field intensity in the surface area of the cathode is the high current density and active material Exchange diffusion;the main reason for the high intensity of the flow field in the surface area of the anode is that the generation of gas on the surface of the anode leads to the enhanced adsorption-desorption effect in this area. |
