Electron microscopic studies on the effect of Sn addition on the ageing characteristics of Al-0.7% Mg2Si alloy

The effect of trace addition of Sn on the ageing characteristics of Al-0.7% Mg₂Si has been studied by hardness measurements and transmission electron microscopy. The changes observed in the microstructural features have been explained on the basis of the strong interaction existing between Sn atoms and quenched-in vacancies. At ageing temperatures below 200°C Sn addition brings about a ratardation in the kinetics of G.P. zone growth whereas at higher ageing temperatures, it aided the precipitate nucleation and growth. The hardness data agree well with the deductions based on observations made on the thin foils.