Magnesium additions to aluminum enhance strength and hardness, lowering density, and improve corrosion resistance. However, during melting and casting processes, significant amounts of magnesium are lost due to selective oxidation. Preventing these losses would reduce the production cost and improve the quality of the final product. / The effects of various levels of strontium addition on the oxidation behaviour of aluminum-magnesium alloy melts were investigated by monitoring sample weight gains with time using a thermogravimetric balance at 750°C. Sample cross-sections have been examined in detail using Hitachi S-4700 Field Emission Gun Scanning Electron Microscope, and phases formed on the oxide layer and in the alloy morphology were identified by EDS, WDS and low angle X-ray diffraction techniques. It was observed that in the absence of Sr, the Al-Mg samples gained substantial amounts of weight by formation of spinel (MgAl2O4) phase at the oxide-metal interface. Samples containing Sr had significantly lower weight gains. The drop in total weight gain by Sr additions was about 98% in low Mg-containing Al-Mg alloys. This change in oxidation behavior was linked to the presence of a Sr-enriched liquid phase underneath the first formed MgO layer, suppressing the formation of spinel crystals. In addition, spherical equilibrium shapes are found in the different as-cast and oxidized alloys of Al-Mg-Sr.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.102689 |
| Date | January 2006 |
| Creators | Ozdemir, Ozgur. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Mining, Metals and Materials Engineering.) |
| Rights | © Ozgur Ozdemir, 2006 |
| Relation | alephsysno: 002571556, proquestno: AAINR27826, Theses scanned by UMI/ProQuest. |
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