Understanding the role of oxidation in bonding of aluminium alloys
<p>The main aim of this work is to study the bonding behaviour of Al alloys as a function of temperature, time and processing conditions from a perspective of oxidation so as to gain a comprehensive knowledge of the oxidation issues during processing and to design better bonding approaches for...
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| Format: | Thesis |
| Language: | English |
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2014
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| _version_ | 1797101370948452352 |
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| author | Wu, G |
| author2 | O‘Reilly, K |
| author_facet | O‘Reilly, K Wu, G |
| author_sort | Wu, G |
| collection | OXFORD |
| description | <p>The main aim of this work is to study the bonding behaviour of Al alloys as a function of temperature, time and processing conditions from a perspective of oxidation so as to gain a comprehensive knowledge of the oxidation issues during processing and to design better bonding approaches for different alloy systems.</p> <p>Two major parts of work have been carried out during the study: (a) the use of a stacking approach and a double pouring approach to potentially join two Al alloys and their effectiveness are assessed; and (b) a precise investigation of the oxidation mechanisms for Al-Cu and Al-Mg alloys using a combination of theoretical analysis and experimental characterization.</p> <p>The project started with the use of a stacking approach to try to bond two stacked Al alloys. The stacked sample can be viewed as a bi-metal which has an oxide <em>bi-film</em> layer at the bond interface. It was found that the <em>bi-film</em> layer was a physical barrier preventing direct metallic bonding. How this <em>bi-film</em> layer evolves during the bonding process was then investigated.</p> <p>The work then moved on to investigate the oxidation mechanisms of Al-Cu alloys and Al-Mg alloys in greater detail. The thermodynamics, kinetics of oxidation, chemistry and morphology of the oxide scale were particularly studied. Briefly speaking, in the case of the Al-Cu-O<sub>2</sub> system, the oxidation proceeds in the order of amorphous γ-Al<sub>2</sub>O<sub>3</sub> - to - crystalline γ-Al<sub>2</sub>O<sub>3</sub> - to - α-Al<sub>2</sub>O<sub>3</sub>; in the case of the Al-Mg-O<sub>2</sub> system, the oxidation proceeds as amorphous γ-Al<sub>2</sub>O<sub>3</sub> to MgO to MgAl<sub>2</sub>O<sub>4</sub> and the morphology of the oxide scale develops from a protective layer to a porously structured composite layer.</p> <p>A double pouring approach was finally developed to bond Al and Al-5Cu but the method has still not been perfected due to the formation of <em>bi-film</em> defects along the bond interface. Induction melting, squeeze casting, and extrusion bonding were therefore studied as an attempt to reduce the harmful effect of <em>bi-film</em> defects. Although all of the approaches exhibit some limitations, they have potential for future development.</p> |
| first_indexed | 2024-03-07T05:50:56Z |
| format | Thesis |
| id | oxford-uuid:e8d98c0a-f8a8-4ea5-9906-94e7be782f7b |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T05:50:56Z |
| publishDate | 2014 |
| record_format | dspace |
| spelling | oxford-uuid:e8d98c0a-f8a8-4ea5-9906-94e7be782f7b2022-03-27T10:49:52ZUnderstanding the role of oxidation in bonding of aluminium alloysThesishttp://purl.org/coar/resource_type/c_db06uuid:e8d98c0a-f8a8-4ea5-9906-94e7be782f7bMaterials SciencesEnglishOxford University Research Archive - Valet2014Wu, GO‘Reilly, KGalano, M<p>The main aim of this work is to study the bonding behaviour of Al alloys as a function of temperature, time and processing conditions from a perspective of oxidation so as to gain a comprehensive knowledge of the oxidation issues during processing and to design better bonding approaches for different alloy systems.</p> <p>Two major parts of work have been carried out during the study: (a) the use of a stacking approach and a double pouring approach to potentially join two Al alloys and their effectiveness are assessed; and (b) a precise investigation of the oxidation mechanisms for Al-Cu and Al-Mg alloys using a combination of theoretical analysis and experimental characterization.</p> <p>The project started with the use of a stacking approach to try to bond two stacked Al alloys. The stacked sample can be viewed as a bi-metal which has an oxide <em>bi-film</em> layer at the bond interface. It was found that the <em>bi-film</em> layer was a physical barrier preventing direct metallic bonding. How this <em>bi-film</em> layer evolves during the bonding process was then investigated.</p> <p>The work then moved on to investigate the oxidation mechanisms of Al-Cu alloys and Al-Mg alloys in greater detail. The thermodynamics, kinetics of oxidation, chemistry and morphology of the oxide scale were particularly studied. Briefly speaking, in the case of the Al-Cu-O<sub>2</sub> system, the oxidation proceeds in the order of amorphous γ-Al<sub>2</sub>O<sub>3</sub> - to - crystalline γ-Al<sub>2</sub>O<sub>3</sub> - to - α-Al<sub>2</sub>O<sub>3</sub>; in the case of the Al-Mg-O<sub>2</sub> system, the oxidation proceeds as amorphous γ-Al<sub>2</sub>O<sub>3</sub> to MgO to MgAl<sub>2</sub>O<sub>4</sub> and the morphology of the oxide scale develops from a protective layer to a porously structured composite layer.</p> <p>A double pouring approach was finally developed to bond Al and Al-5Cu but the method has still not been perfected due to the formation of <em>bi-film</em> defects along the bond interface. Induction melting, squeeze casting, and extrusion bonding were therefore studied as an attempt to reduce the harmful effect of <em>bi-film</em> defects. Although all of the approaches exhibit some limitations, they have potential for future development.</p> |
| spellingShingle | Materials Sciences Wu, G Understanding the role of oxidation in bonding of aluminium alloys |
| title | Understanding the role of oxidation in bonding of aluminium alloys |
| title_full | Understanding the role of oxidation in bonding of aluminium alloys |
| title_fullStr | Understanding the role of oxidation in bonding of aluminium alloys |
| title_full_unstemmed | Understanding the role of oxidation in bonding of aluminium alloys |
| title_short | Understanding the role of oxidation in bonding of aluminium alloys |
| title_sort | understanding the role of oxidation in bonding of aluminium alloys |
| topic | Materials Sciences |
| work_keys_str_mv | AT wug understandingtheroleofoxidationinbondingofaluminiumalloys |