Study On The Preparation And Mechanism Of Al(Mg)-Nd Alloys In Molten Salt

With the development of high-tech industries, the lightest apparatus and devices have attracted the extensive concern of scholars. The most representative lightest materials are aluminum and magnesium alloys, which have the advantages of low density, high specific rigidity, prominent damping performance and excellent electromagnetic shielding performance.However, the low strength and poor corrosion resistance limits their further application. Adding metallic elements, especially the rare earth elements, is one of the most effective methods to improve their performance. Compared with the typical method of directly mixing and fusing the metallic element, preparation of rare earth (RE) alloy by molten salt electrolysis is the hot topics of the society. Therefore, the element neodymium was selected as the metallic elements. The electrochemical behavior of Nd(?) ions was studied by different electrochemical measurements in LiCl-KCl-MgCl2-AlCl3 melts on a W electrode and in LiCl-KCl melts on active aluminum and magnesium electrodes, respectively. The prepared Al-Nd and Mg-Nd alloys were finally analyzed by XRD and SEM equipped with EDS analysis.1. The electrochemical behavior of Nd(?) ions in LiCl-KCl melts on a W electrode was studied by cyclic voltammetry, square wave voltammetry and open circuit chronopotentiometry.The results illustrated that Nd(?) reduction to metal Nd is through by two step reactions. The transfer electron numbers were finally determined by square wave voltammetry. In LiCl-KCl-AlCl-3NdCl3 melts, when the reduction potentials were -1.39 and -1.47 V, two kinds of Al-Nd alloys could be formed. These Al-Nd alloys were formed by the underpotential deposition of Nd(?) on the aluminum already coated on the W electrode. Two kinds of signals corresponding to Al-Nd alloys were also obtained on the aluminum electrode. The Al-Nd alloys were prepared by potentiostatic electrolysis at -2.0 V for 6 h. The XRD analysis displayed that the Al-Nd alloys were composed by Al2Nd phase.2. In LiCl-KCl, the diffusion coefficients and reversibility of Al(?) on the W electrodewere measured by different electrochemical measurements. The AlCl3 as chlorinating agent, the solubility of Nd2O3 was studied in LiCl-KCI-AlCl3 melts at different experimental temperatures.The results exhibited that the solubility of Nd2O3 increased with increase of the experimental temperature. At 873 K, the concentration of Nd(?) was maximum. At the asme time, this result was verified by the solid state reaction of Nd2O3(s)+Al2Cl3(g,l)?Al2O3(s)+2NdCl3(s). The reduction process of Nd(?) ions was investigated by different electrochemical measurements in LiCl-KCl-AlCl3 melts on a W electrode and in LiCl-KCl melts on active aluminum electrode,respectively. The Al-RE based alloys with Al2Nd and Al3Nd phases were prepared by galvanostatic electrolysis both on the W and Al electrodes. The alloys were finally examined by XRD and SEM equipped with EDS analysis, respectively.3. In LiCl-KCl melts, the diffusion coefficients and reversibility of Mg(?) on the W electrode were analyzed by different electrochemical measurements. Both on W and Mg electrodes, two kinds of reduction signals corresponding to the formation of Mg-Nd alloys could be observed. The Mg-Nd alloys were prepared by potentiostatic electrolysis on the Mg electrode and galvanostatic electrolysis on the W electrode, respectively. The obtained Mg-Nd alloys were analyzed by XRD analysis. The XRD pattern illustrated that the Mg-Nd alloy prepared by galvanostatic electrolysis was composed by Mg4iNds phase and the Mg-Nd alloy obtained by potentiostatic electrolysis comprised Mg12Nd and Mg4iNds phases. This result suggested that the content of Nd in Mg-Nd alloy increased when the potential shifted negative.