Pre-Ageing to Improve the Microstructure and Tensile Properties of Al-0.72Mg-0.42Si-0.1Cu Artificially Aged Alloy

Abstract This paper describes a low temperature pre-ageing method that can improve the strength of artificially aged Al-Mg-Si-Cu alloys. The precipitation behaviour of the alloy samples was analyzed by use of differential scanning calorimetry (DSC) and the results were confirmed by microstructural observations using high resolution transmission electron microscopy (HRTEM). Tensile testing was performed to determine the mechanical properties of the samples. The results indicate that GP zones (I) formed in the alloy matrix with either natural ageing or pre-ageing at 50 °C and the formation of GP zones (I) retarded precipitation of the β'' phase during artificial ageing: it can be concluded that increasing the holding period would significantly decrease the strength after artificial ageing at 170 °C. Pre-ageing either at 70 or 90 °C, however, immediately after quenching of nuclei for precipitation of the β'' phase formed in the alloy matrix, showed that the precipitate particles formed in the pre-ageing cond...