Affiliation:
1. SINTEF Materials and Chemistry
2. Norwegian University of Science and Technology
Abstract
Thermal oxidation of a 3000 Al sheet rolled alloy was carried out in various atmospheres with a thermogravimetric analyzer (TGA). The effect of a flash anodized surface versus an untreated rolled surface is investigated. All samples were oxidized for 4 hours at 800°C. Samples oxidized in air, 100 % CO2 and 50% CO2–50% air, showed no difference in total oxidation. The flash anodized samples oxidized in 10% CO2–90% air had approximately half of the mass gain of the rolled samples. Oxidation of anodized samples in pure oxygen and nitrogen showed a drastic decrease in the amount of mass gained compared to the other atmospheres. Flash anodized samples gave consistent results, and the oxidation behavior tended to be linear or S-shaped for the 4 hours investigated. Rolled samples gave less consistent data and tended to be decelerating curves. Transmission electron microscope (TEM) analysis of the oxide layer before and after showed magnesium diffusion toward the surface of the sample, with a steep gradient over a distance of 400 µm. The flash anodized oxide layer was often difficult to find, having been removed during of the TEM sample preparation, but was found to double in size from 200 to 400 µm when located.
Publisher
Trans Tech Publications, Ltd.
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics,General Materials Science
Reference5 articles.
1. D. Stevens, A. Kvithyld, T. A. Engh, S. Wilson, Oxidation of AlMg in Dry and Humid Atmospheres, TMS Light Metals (2011).
2. ASM International Handbooks Online, www. asminternational. org, accessed April 29, (2011).
3. Michael E. Brown, Introduction to Thermal Analysis, 2nd edition (Kluwer Academic Publishers, 2001).
4. Robert F. Speyer, Thermal Analysis of Materials (CRC Press 1993).
5. T.S. Shih, I. C. Chen, Decomposition and Reaction of Thermal-Formed Alumina in Aluminum alloy Castings, Materials Transactions, 46, (2005), 1868-1876.