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The Effect of Microstructures on the Corrosion Behaviors of Aluminum and Aluminum Alloy

Author: WeiLiYan
Tutor: MengGuoZhe
School: Harbin Engineering University
Course: Materials Science
Keywords: mcrocrystallinzation nanoscale twins aluminum alloy intermetallic components corrosion stochastic analysis
CLC: TG171
Type: Master's thesis
Year: 2009
Downloads: 428
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Abstract


The mechanics, physical, chemical and electrochemical performance of materials were determined not only by their composition but also their microstructures. The corrosion behaviors of microcrystalline materials and nanocrystalline materials with twin structures are different from that of polycrystalline materials. The intermetallic components of materials also affect the corrosion behaviors. In our work, microcrystalline aluminum （MC Al） and nanocrystalline aluminum with twins （NT Al） coating were synthesized using magnetron sputter technique by optimizing the plating parameters. Transmission electron microscopy （TEM） was used to characterize the microstructure of the MC Al and NT Al coating samples. The grain size of MC Al coating about 400 nm , the grain size of the NT Al coating samples was about 100 ran and the distance between twins was about 30～50 nm.One object of this work is focus on the corrosion behaviors of MC Al and NT Al coating in the NaCl acidic solution. Electrochemical methods such as potentiodynamic polarization curves, impedance spectrum （EIS）, electrochemical noise （EN） were employed in this work. The results indicated that the corrosion potentials of the MC Al and NT Al coating became more positive and their corrosion current densities decreased; MC Al and NT Al coating showed obvious passive characteristic. There are two kinds of effect for microcrystallization and nanoscale twin structure on the pit behavior of pure aluminum: （1） the rate of pit initiation was accelerated; （2） the pit growth was impeded. This leads to the enhancement of pitting resistance for microcrystallized aluminum and pure aluminum with nanoscale twins.The second object of this work is focus on researching the corrosion of aluminum alloy LY12 under thin electrolyte layers with various thickness. The experiments were carried out in neutral sodium chloride solutions by cathodic polarization, electrochemical impedance spectroscopy （EIS） and electrochemical noise （EN）.The results revealed that with the increasing of thin layer thickness, both cathodic and anodic process of the corrosion of aluminum alloy LY12 were inhibited. The corrosion type was more uniform in bulk solution than that under thin layer.The intermetallic components Al2Cu and Al2CuMg increased the localized corrosion of aluminum alloy LY12.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metal corrosion protection,metal surface treatment > Theory of metal corrosion
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