Influence Of External Field On The Structure And Performance Of Fe-based Amorphous Alloy

As a new kind of structural and functional material, iron based metallic glasses possess not only extreme strength and abrasive resistance, but also excellent magnetic properties, which have wide application prospects. In the present thesis, the influences of external field on the glass-forming ability, corrosion resistance, thermal stability, magnetic properties and microstructure of Fe78Si9B13metallic glass were investigated.Pressure treatment was imposed on the ribbons of Fe78Si9B13metallic glass with different values of pressure. The microstructures were investigated by XRD and SEM. The thermal stability, crystallization behavior, and thermal expansion behavior were analyzed by DSC and DIL. Corrosion resistance was studied through electrochemical corrosion of the sample in different electrolyte, and the change of electrical resistivity was also studied. By these different measurements, it is known that the amount of free volume in the metallic glass increases with the increase of pressure, which results in the increase of electrical resistivity and the decrease of corrosion resistance. But under high pressure, Si atoms move into the free volume, which decreases the electrical resistivity and increases the corrosion resistance.The electrochemical corrosion was imposed with different electrolytes (NaOH, NaCl, and H2SO4solutions) with magnetic field, and the corresponding polarization curves were obtained. The surface topographies of the alloys were analyzed. According to the results, the influences of magnetic field on corrosion behaviors of the metallic glasses in different electrolytes can be classified as two kinds. With magnetic field in the low electrolytes, the dissolution rate was accelerated and thus deepens the corrosion degree. But in the high solution, the magnetic field can influence the movement of the ions of metals and solutions. According to the magnetofluid dynamics, the ions under Lorentz force will gather on the surface of samples, protect the surface from dissolving, and thus increase the corrosion resistance.Because of the different cooling rates in the center and margin regions of the glass ribbons, through different measurements (VSM, SEM, TEM, DSC, and electrochemical corrosion), these two regions were analyzed. Results showed that cooling rates can influence the GFA and microstructures, and the corrosion resistance of the center region is higher. The nervation lines were much denser in the center region through fracture surface scanning. In addition, there are some slippage plats for the alloy center region. All these results showed that the plasticity of the center region is much better.