Effect of Melt Temperature on Surface Films Formed on Molten AZ91D Alloy Protected by Graphite Powder
| Autor: | Jixue Zhou, Baichang Ma, Weihong Li, Yuansheng Yang, Jianhua Wu, Jinwei Wang |
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| Rok vydání: | 2017 |
| Předmět: |
Materials science
Scanning electron microscope 020502 materials Alloy Metallurgy Metals and Alloys chemistry.chemical_element 02 engineering and technology engineering.material 021001 nanoscience & nanotechnology Condensed Matter Physics Microstructure Casting 0205 materials engineering chemistry Mechanics of Materials Aluminium Oxidizing agent Materials Chemistry engineering Graphite Composite material 0210 nano-technology Carbon |
| Zdroj: | Metallurgical and Materials Transactions B. 48:3152-3160 |
| ISSN: | 1543-1916 1073-5615 |
| Popis: | Graphite powder was adopted to prevent AZ91D alloy from oxidizing during melting and casting. The microstructure of the resultant surface films, formed at 933 K, 973 K, 1013 K, and 1053 K (660 °C, 700 °C, 740 °C, and 780 °C) for 30 minutes, was investigated by scanning electron microscopy, energy dispersive spectrometer, and X-ray diffraction, and the phase composition of the surface films was analyzed by the standard Gibbs free energy change of the reactions between the graphite powder, the alloy melt, and the ambient atmosphere. The effect and mechanism of melt temperature on the resultant surface films were also discussed. The results indicated that the surface films, of which the surface morphology comprised folds and wrinkles, were composed of a protective layer and MgF2 particles. The protective layer was contributive to the prevention of the molten alloy from oxidizing, and consisted of magnesium, oxygen, fluorine, carbon, and a small amount of aluminium existing in the form of MgO, MgF2, C, and MgAl2O4. The layer thickness was 200 to 900 nm. The melt temperature may affect the surface films through the increased interaction between the graphite powder, the melt, and the ambient atmosphere. The oxygen content and thickness of the protective layer decreased and then increased, while the height of the folds increased with melt temperature. |
| Databáze: | OpenAIRE |
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