In this paper, the effect of trace Sn on the precipitation behavior and mechanical properties of Al–Mg–Si alloys with different Mg/Si ratios aged at 180 °C was investigated using hardness measurements, a room-temperature tensile test, transmission electron microscopy and differential scanning calorimetry. The results shown that Sn reduces the precipitation activation energy, increases the number density of β″ precipitates, and then increased the aging hardenability and mechanical properties of the Al–Mg–Si alloy. However, the positive effect of Sn on the mechanical properties of the Al–Mg–Si alloy drops with the decrease of the Mg/Si ratio of the alloy.

The large-scale quantitative analysis of α- and β-AlFeMnSi particles present in wrought aluminum alloys through chemical composition analysis is inefficient and time consuming. The morphology and size of α- and β-AlFeMnSi particles in an Al-Mg-Si wrought alloys are quantitatively investigated in this study. The length and width data of the particles were analysed by image processing from scanning electron microscopy and back-scattered electron images. A bimodal distribution of the length:width (l:w) ratio is found by removing ultrafine particles. The model with smaller average l:w ratio is found to be α-AlFeMnSi particles, and the model with larger average l:w ratio is found to be β-AlFeMnSi particles. A critical length:width ratio, which is found to be 2.7 in this paper, is used to discriminate α-AlFeMnSi particles from β-AlFeMnSi particles. In comparison to the EDS results, the α- and β-AlFeMnSi particles can be effectively determined using the l:w ratio with an accuracy rate of up to 95.3.