There is a great need in the transportation industry for high strength, high stiffness and lightweight materials with excellent dimensional stability. The use of these materials reduces fuel consumption and greenhouse gas emission as well as malfunctioning of components when subjected to fluctuating temperatures. Metal matrix composites (MMCs) are designed to meet these needs of transportation and other industries. However, their use is limited by lack of information on their thermal behaviour. In addition, reactions that occur in MMCs alter their microstructure and properties. These reactions have been widely investigated using X-ray Diffractometry (XRD) and electron microscopy (EM). However, these techniques cannot provide information such as charge transfer and local elemental structures in materials. Synchrotron X-ray Absorption Spectroscopy (XAS) could be used to identify reaction products in MMCs as well as provide information which XRD and EM cannot provide.<p>
The thermal behaviour of Al-Mg alloy A535 containing fly ash particles as well as charge transfer and reactivity in particulate aluminium alloy metal matrix composites (MMCs) were investigated in this work. The materials studied were (i) Al-Cu-Mg alloy AA2618 and its composites reinforced with 10 and 15 vol.% alumina (Al2O3) particles and (ii) Al-Mg alloy A535 and its composites reinforced with a mixture of 5 wt.% fly ash and 5 wt.% silicon carbide, 10 wt.% and 15 wt.% fly ash. The investigative techniques used included Differential Scanning Calorimetry (DSC), Thermomechanical Analysis (TMA), Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and synchrotron X-ray Absorption Spectroscopy (XAS).<p>
The results obtained showed that the coefficient of thermal expansion (CTE) of A535 decreased with the addition of fly ash and silicon carbide. Also, the addition of these particles improved the dimensional stability of the alloy in that the residual strain, åp, cycling strain, åc, and CTE decreased. The results obtained from XAS measurements showed evidence of charge redistribution in the aluminium in AA2618 with the addition of alumina particles. The results obtained from XAS measurements showed evidence of charge redistribution in the aluminium in AA2618 with the addition of alumina particles. The addition of alumina particles into AA2618 increased the p-orbital population and also changed the surface chemistry of the matrix. It was also demonstrated that the XAS technique can be used to determine the presence of various oxides in industrial fly ash and spinel (MgAl2O4) in alumina and fly ash particles extracted from the MMCs.
| Identifer | oai:union.ndltd.org:USASK/oai:usask.ca:etd-04132009-150155 |
| Date | 20 April 2009 |
| Creators | Uju, Williams Alozie |
| Contributors | Sammynaiken, Ramaswami, Oguocha, Ikechukwuka N., Torvi, David A. |
| Publisher | University of Saskatchewan |
| Source Sets | University of Saskatchewan Library |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-04132009-150155/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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