Studies On The Preparation Of Fe-6.5wt%Si Sheet By Molten Salts Electrodeposition

Fe-6.5wt%Si alloy is fit for the application of the magnetic screen and iron core used in high speed electric machine; low noise and low potential transformer, because of the alloy have the excellent electromagnetism performance: low magnetocrystalline anisotropy, near zero magnetostriction coefficient and high electrical resistivity. But its plasticity and mechanical properties are hard and brittle to be worked into sheet form. In recent years, people are seeking for a good method to produce the Fe-6.5wt%Si sheet all the times. In this paper, Fe-6.5wt%Si sheet was produced on the Fe-3wt%Si sheet by electrodeposition in molten salts, which was a new method for producing the Fe-Si binary alloy sheet.In this paper, the studies were carried on FLINAK molten salt containing 6mol% Na2SiF6. Cyclic voltammetry, chronopotentionmetry and chronoamperometry were employed to investigate the electrochemical mechanism and electrocrystallization process of silicon ion electrodeposition in FLINAK molten salts. It was found that the electrode process was a reversible electrode process which controlled by diffusion process, and the product was infusible; the diffusion coefficient of silicon ion in molten salts was measured as 5.42×10^-7cm²/s(750℃). The electrocrystallization process of silicon was hemispherical three-dimensional nucleus continuous growth mechanism; and increasing overpotential properly was benefit for the increase in nucleus density which was good for getting high quality coating.The technological parameters of silicon electrodeposition were studied in the FLINAK molten salts. The metallurgical structures of the silicon coating were shown by the metallurgical microscope and scanning electron microscope. The optimum composition and temperature were determined as follows: the concentration of Na2SiF6 was 6⁸mol%; and the temperature was about 730⁷80℃. A thicker silicon coating about 20⁷0μm in thickness was obtained by pulsing current compared with direct current deposition.The silicon contents of coating were shown by glow-discharge spectrometer, and the metalliding process was discussed. The conditions of the annealing diffusion and siliconizing were given by preparation of Fe-6.5wt%Si sheet, the diffusion behaviors of Si atoms in Fe matrix were simulated by computer. The Fe-6.5wt%Si sheet were prepared from Fe-3wt%Si sheet by annealing diffusion treatment in 1050℃.