Effects of homogenisation treatment on microstructure and hot ductility of aluminium alloy 6063

Abstract

Several homogenisation treatments were applied to direct chill (DC) cast ingots of aluminium alloy 6063, in order to analyse the resulting microstructures developed from these diverse conditions and their effects on the hot ductility of this alloy. Imaging was performed using scanning electron microscopy (SEM) and a focused ion beam (FIB) instrument. These techniques identified variations in distribution and morphology of second phase particles (AlFeSi and Mg2Si). FIB results for the various AlFeSi particles correctly identify their shapes in three dimensions (3D). The particles were identified by energy dispersive spectroscopy (EDS) in the SEM, and by X-ray diffraction (XRD) for bulk samples. Hot tensile testing (HTT) was conducted between 470 and 600°C to asses the hot ductility for each condition. The inferior ductility of as cast samples was due to the poor bond strength of the β AlFeSi phase at the grain boundaries. Homogenised samples, which contain α AlFeSi, exhibited improved ductility. Samples that were water quenched following homogenisation were absent of Mg2Si precipitates, when these elements remained in solid solution. These exhibited the highest ductility.