Study On Component Action,structural Characteristics Of Aluminum-based Amorphous Alloys And Preparation And Sealing Treatment Of Coatings

Al-based amorphous alloys,possessing higher strength-to-weight ratio,better resistance to wear and corrosion,more flexible alloy composition design than conventional crystalline aluminum alloys,can be used as the protective coatings in wear and corrosion fields.In this paper,the composition optimization,structure selection,spraying process parameters selection and post-treatment of Al-based amorphous coatings were studied.Finally,the Al-based amorphous coating with low porosity,high amorphous content and good corrosion resistance was successfully prepared..In the role of alloy components,we found that microalloying with either Ti or Cr could greatly improve the corrosion resistance of Al-Ni-Y amorphous alloys.The passive current densities were reduced by one order of magnitude by the addition of Ti or Cr.The concentration of Ti or Cr in the outmost layer of passive films is higher than that in the amorphous substrate as demonstrated by the XPS results,which was responsible for the increased film resistance and thereby the improved corrosion resistance.At the same time,we also studied the effect of Ce content on the corrosion behavior of the Al-Co-Ce amorphous alloy.The Al-Co-Ce amorphous alloy with 4 at.%Ce displayed the best corrosion resistance,and the addition of excess Ce led to the reduced corrosion resistance.The Al-Co-Ce amorphous alloys with a low Ce content were prone to form a more protective passive film,thereby a better corrosion resistance.With regard to structure tailoring,we investigated the effect of structural evolution on the corrosion behavior of Al-Ni-Y amorphous alloy,and discussed the relevant mechanisms.A structural relaxation annealing(150?,5min)below Tg could significantly enhance the corrosion resistance of Al-Ni-Y alloy.This improved resistance to corrosion was closely related to the reduction of VF,which facilitates the formation of a highly protective passive film.As for the partially devitrified alloys,their electrochemical corrosion behavior was closely associated with the nanocrystal size.There existed a critical nanocrystal size,above which the corrosion resistance of Al-based amorphous alloy was remarkably reduced,while the corrosion resistance was unchanged when the nanocrystal size is below the critical size range.As to the optimization of spraying parameters,we prepared the amorphous coatings with diflferent spraying parameters and characterized their structure and corrosion resistance.The optimum parameter of HVAF spraying is air-to-fuel 96/90,spraying distance 165 mm,powder feeding 4 r/min and turntable speed 3.9 m/s.In the section of post-treatment of Al-based amorphous coating,we further improved its corrosion resistance through sealing treatment.We studied the sealing effect of three kinds of sealants.The sealing effect was as follows:stearic acid>potassium dichromate>nickel acetate based on the long-term electrochemical tests.Stearic acid had the best sealing effect because of its good impermeability and hydrophobicity.