Effects Of Mg, Si And Cu On Ageing Response Of Dilute 6xxx Series Aluminium Alloys

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dc.contributor.authorJaafar, Che Nor Aiza
dc.date.accessioned2018-06-25T06:55:37Z
dc.date.available2018-06-25T06:55:37Z
dc.date.issued2011-02
dc.description.abstractThe effects of magnesium (Mg), silicon (Si) and copper (Cu) on ageing response of heat treatable dilute 6xxx series aluminium alloys have been investigated. The alloys contained between 0.22 to 0.79 wt% Si and 0.20 to 0.51 wt% Mg. In this study, some alloys contained 0.1 wt% Cu and others contained 0.001 to 0.002 wt% Cu which were considered as Cu-free alloys. In order to study the effect of composition on the ageing response, the alloys samples were solution treated at 530  5 oC for 5 minutes and then water quenched into ice water at 0 oC before naturally aged at room temperature and artificially aged at elevated temperature. The effects of natural ageing and artificial ageing on the ageing response were investigated using Vickers hardness test and tensile test, respectively. The microstructures of artificially aged alloys were investigated by transmission electron microscopy (TEM). The results showed a correlation between ageing response and composition, hardness, strength and microstructure of the alloys. The higher solute contents of Mg2Si and Silicon in excess (ExSi) in the alloys produced higher hardness and tensile strength and consequently the strongest ageing response. Addition of small Cu content (0.1 wt%) gave only a slight increase in hardness, strength and ageing response during artificial ageing but not in the case of natural ageing. The TEM results revealed that the precipitates formed during artificial ageing at 185 oC were needles and at 300 oC were needles and rods with their major axes parallel to [100] of the matrix direction. The number density of precipitates increased as their solute content of Mg2Si and ExSi increased. Addition of 0.1 wt% Cu refined the precipitates and increased slightly the number density of precipitates in the dilute alloys. It was found that prolong ageing time for 1000 hours at 300 oC resulted in the formation of coarse precipitates in the most of over-aged alloys. Analysis by TEMEDX on coarse precipitates of over-aged alloy of alloy Al-0.50wt%Mg-0.76wt%Si indicates that Mg2Si, AlFeSi, -AlMnSi and Si precipitates were coexist in this alloy.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/5773
dc.language.isoenen_US
dc.publisherUniversiti Sains Malaysiaen_US
dc.subjectThe effects of magnesium (Mg), silicon (Si) and copper (Cu) on ageingen_US
dc.subjectresponse of heat treatable dilute 6xxx series aluminium alloysen_US
dc.titleEffects Of Mg, Si And Cu On Ageing Response Of Dilute 6xxx Series Aluminium Alloysen_US
dc.typeThesisen_US
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