A TEM study of precipitation in Al-Mg-Si alloys

A set of extrusion samples of Al-Si-Mg alloys (0.5 wt%Mg and 0.3-0.8 wt%Si) were, respectively, T1- and T4-heat-treated. Differential scanning calorim etry (DSC) was used to heat the samples to particular temperatures to promo te the formation of precipitates for study by transmission electron microsc opy (TEM). It was found that, apart from beta ", beta', and B', there were many precipitates showing rectangular lattices when viewed along the long a xes of the precipitates. It is considered that the residual stresses (or di slocations) in the extrusion after the TI-treatment facilitated the nucleat ion and growth of the precipitates during the heating in the DSC. (C) 2001 Elsevier Science Ltd. All rights reserved.