A method to study the history of a double oxide film defect in liquid aluminum alloys |
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Authors: | R Raiszadeh PhD W D Griffiths |
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Affiliation: | (1) the Department of Metallurgy and Materials Science, School of Engineering, University of Birmingham, B15 2TT Edgbaston, Birmingham, United Kingdom;(2) the Department of Materials Science and Engineering, Shahid Bahonar University of Kerman, Kerman, Iran;(3) the Department of Metallurgy and Materials Science, School of Engineering, University of Birmingham, UK |
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Abstract: | Entrained double oxide films have been held responsible for reductions in mechanical properties in aluminum casting alloys.
However, their behavior in the liquid metal, once formed, has not been studied directly. It has been proposed that the atmosphere
entrapped in the double oxide film defect will continue to react with the liquid metal surrounding it, perhaps leading to
its elimination as a significant defect. A silicon-nitride rod with a hole in one end was plunged into liquid aluminum to
hold a known volume of air in contact with the liquid metal at a constant temperature. The change in the air volume with time
was recorded by real-time X-ray radiography to determine the reaction rates of the trapped atmosphere with the liquid aluminum,
creating a model for the behavior of an entrained double oxide film defect. The results from this experiment showed that first
oxygen, and then nitrogen, was consumed by the aluminum alloy, to form aluminum oxide and aluminum nitride, respectively.
The effect of adding different elements to the liquid aluminum and the effect of different hydrogen contents were also studied.
This article is based on a presentation made in the John Campbell Symposium on Shape Casting, held during the TMS Annual Meeting,
February 13–17, 2005, in San Francisco, CA. |
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