HRTEM and HAADF-STEM of precipitates at peak ageing of cast A319 aluminium alloy

High-resolution transmission electron microscopy (HRTEM) and high-angle annular-dark-field scanning transmission electron microscopy (HAADF-STEM) were applied to investigate the precipitates formed during age hardening at 170 +/- 5 degrees C for up to 48 h of cast A319 aluminium,alloy (Al-4.93 wt%Si-3.47 wt%Cu). The precipitates at the peak-aged condition have been identified as mainly theta '' together with a smaller amount of theta'. It is proposed that the theta '' is responsible for hardening at peak ageing at 170 degrees C of the cast A319 aluminium alloy. (C) 2012 Elsevier Ltd. All rights reserved.