Precipitation of the metastable phases in a tin microalloyed Al-10at%Ag alloy

The formation of the metastable phases in aluminium alloys is closely linked with the excess vacancies. Traces of tin added to an Al-Ag alloy exert an influence on the precipitation kinetics. In the quenched Al-Ag alloys, the precipitation is controlled by the diffusion of solute atoms which require the presence of free vacancies. Due to their high binding energy with vacancies, tin atoms modify the nucleation and growth characteristics of the phases which form during precipitation. Tin atoms retard the precipitation of the Guinier-Preston zones at 90, 125 and 150 °C, suppresses it at 170 and 200 °C and, at all temperatures, stimulate the precipitation of the metastable γ’ phase.