二元双相块体纳米晶Ag-25Ni合金腐蚀性能研究
[Abstract]:The study on the stability of nanomaterials in various solutions has attracted much attention. Up to now, the researches in this field have mainly focused on the surface nanocrystalline, nanocrystalline films and nanocrystalline coatings at home and abroad, but the corrosion properties of bulk, especially bulk nanocrystalline binary dual phase alloys, have been relatively few. Nanocrystalline Ag-25Ni alloy powder was prepared by mechanical alloying method (MA) and liquid phase reduction method (LPR) by optimizing synthesis parameters. Bulk nanocrystalline Ag-25Ni alloy was prepared by vacuum hot pressing technology by optimizing hot pressing parameters. Compared with the conventional bulk Ag-25Ni alloy prepared by powder metallurgy method (PM), the electrochemical workstation was used to study their effect on neutral NaCl, by means of polarization curve, AC impedance spectrum, average activation energy and Mott-Schottky curve. The corrosion resistance of H_2SO_4 and acid NaCl solution and the effect of microstructure refinement on their corrosion resistance are discussed. The results show that: (1) the microstructure, phase structure and distribution of the three alloys are different, such as grain size. The microstructure of conventional bulk alloy prepared by powder metallurgy method is very uneven, and the solution between components is very low. The microstructure of bulk nanocrystalline alloy prepared by mechanical alloying method is uniform, and there is a certain solution degree among the components, while the microstructure of bulk nanocrystalline alloy prepared by liquid phase reduction method is uniform, and the solution degree between components is low. (2) the corrosion current density of three kinds of PM Ag-25Ni,LPR Ag-25Ni and MAAg-25Ni alloys prepared by different methods increased after adding NaCl,H_2SO_4 and acidic Na Cl solution to neutral Na_2SO_4 solution, and the corrosion current density increased with the increase of solution concentration. The corrosion current density of the three alloys increased. After grain refinement, the corrosion rate of nanocrystalline MAAg-25Ni alloy decreased, while that of nanocrystalline LPRAg-25Ni alloy accelerated. (3) in neutral NaCl solution, the AC impedance spectra of three kinds of Ag-25Ni alloys prepared by different methods are all composed of single capacitive reactance arc, and the corrosion process is controlled by electrochemical reaction. In H_2SO_4 solution, the AC impedance spectrum of MAAg-25Ni and PMAg-25Ni alloys is single capacitive reactance arc, while that of LPRAg-25Ni alloy is diffusion tail, and the corrosion process is controlled by diffusion. In acidic NaCl solution, the AC impedance of PMAg-25Ni alloy is composed of single capacitive reactance arc, while the diffusion tail of LPRAg-25Ni and MA Ag-25Ni alloys appears. The change trend of charge transfer resistance of the three alloys is opposite to the corrosion current density. (4) in neutral NaCl,H_2SO_4 and acid NaCl solution, the three kinds of Ag-25Ni alloys prepared by different methods all appear passivation phenomenon, the grain refinement does not change the type of passivation film semiconductor, all of them are n-type semiconductors. In neutral NaCl and acidic NaCl solutions, the carrier density of passivated films formed on the surface of the three alloys decreased in the order of LPRAg-25NiPM Ag-25NiMA Ag-25Ni alloys. In H_2SO_4 solution, the carrier density of the passivated film decreases in the order of LPRAg-25NiMAAg-25NiPMAg-25Ni alloy, which is consistent with the law of the magnitude of the three alloys.
【学位授予单位】:沈阳师范大学
【学位级别】:硕士
【学位授予年份】:2017
【分类号】:TB383.1;TG178
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