Effects of composition on the mechanical properties and microstructural development of dilute 6000 series alloys

Abstract

The aim of the present investigation is to study the effect of composition on the mechanical properties and microstructural development during thermal treatment of some dilute 6000 aluminium alloys. The alloys were based on 6000 series dilute aluminium alloys containing different levels of magnesium (Mg) and silicon (Si) contents. The effects of artificial ageing (T6) on the precipitation hardening behaviour were studied in the four dilute alloys. The solution treated alloys samples were quenched at 530°C for 5 min and then immediately subjected to ageing at 185 and 300°C. The ageing response and mechanical propertiesof the alloys were investigated by hardness and tensile test, respectively. The microstructures of the alloys were monitored using Transmission Electron Microscopy (TEM). The results from this study showed a correlation between the Mg and Si contents on themechanical properties and microstructures of the alloys after ageing treatment. It is apparent that an increasing solute content of Mg2Si and ExSi has marked effect in increasing hardness and tensile properties of the alloys. It was found that Mg2Si is more effective than ExSi in hardening and strengthen the alloys. The precipitates formed during artificial ageing were needle-shaped with their major axes parallel to (100) directions of the matrix. The number density of precipitates increased as their solute contents of Mg2Si and ExSi increased. Overall results of TEM observation are in agreement with the results of hardness and tensile test.