The influence of equal channel angular pressing angles on the microstructure and properties of Al-Si-Mg alloy

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dc.contributor.authorAl-Jubouri, Ali Abadi Altayef
dc.date.accessioned2014-11-03T02:26:48Z
dc.date.available2014-11-03T02:26:48Z
dc.date.issued2006
dc.descriptionPhDen_US
dc.description.abstractThe aim of this research is to improve the physical and mechanical properties of Al-Si-Mg alloy by grain structure refinement produced by severe plastic deformation through equal channel angular pressing (ECAP). This alloy has a composition (in wt. %) of 1.3 Si, 0.3 Mg, 0.18 Fe, 0.023 Cu, 0.019 Mn, 0.017 Zn, and 0.014 Ga, 0.011 Ti 1.3 Si, 0.3 Mg, 0.18 Fe, 0.023 Cu, 0.019 Mn, 0.017 Zn, 0.014 Ga, 0.011 Ti balance Al. In ECAP process, the workpieces are pressed through a 1200 and 900 dies using route BC. Through this route the sample is rotated by 900 in the same direction between each consecutive pressing through the ECAP dies. Workpieces undergo plastic deformation by pure shear through the intersecting corner. Microstructure evaluation, physical and mechanical properties of the extruded Al-Si-Mg workpieces by equal channel angular pressing were conducted using scanning electron microscopy (SEM), micro-Vickers hardness tester, tensile test machine, heat conduction apparatus and auto lab corrosion test system. The effect of die angles on the microstructural refinement and mechanical properties at annealing temperature (230 0C and 500 0C) and deformation temperature (600 0C) were investigated. From the microstructure evolution, ECAPed resulted in reduction of grain size from 70-100 m to about 200nm. The ECAPed workpieces that underwent annealing at 500 0C for 24h before ECAP also displayed grains with similar sizes. However, annealing process at 230 0C for 20-30min after ECAP leads to an increase of grain size to around 300 to 600nm. Microhardness was improved by 250-300% and there was slight reduction in its value obtained with the increase in annealing time of ECAPed workpieces. The enhancement of thermal conductivity is by 19-30%, depending on channel angle and annealing conditions. It showed higher value for sharper channel angle (900), and higher annealing temperature. From the tensile tests, the maximum load, maximum stress and elongation to failure increases with the number of passes through the ECAP die. Results from the corrosion experiments of deformed Al-Si-Mg alloy in 3.5% NaCl solution showed better corrosion resistance compared to ascast Al-Si-Mg alloy. The corrosion rate was reduced with the number of passes through the ECAP dies but its value increases with increasing annealing temperature. In general, a drastic change in all investigated mechanical and physical properties occurred after the first pass through the ECAP dies. It is well known that the ECAP provides a simple, cheap and effective processing technique for producing nanostructured Al-Si-Mg alloy. Consequently the improvement in the mechanical and physical properties offers great potential to be used in various industrial applications.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/307
dc.language.isoenen_US
dc.subjectMaterials and Mineral Resources Engineeringen_US
dc.subjectChannel angularen_US
dc.subjectAl-Si-Mg alloyen_US
dc.titleThe influence of equal channel angular pressing angles on the microstructure and properties of Al-Si-Mg alloyen_US
dc.typeThesisen_US
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