The evolution of the microstructure, the chemical composition and the transformation kinetics of primary precipitates from the as-cast Hydro AA 3003 alloy have been studied during isothermal holdings from 400℃ to 600℃. The comparison between the electrical resistivity and microstructure variations obtained by image analysis and in situ TEM has allowed to establish clear correlations. The chemical composition of the particles measured by TEM-EDX show that the ratio Mn/(Mn+Fe) of the Al{sub}6(Mn,Fe) and a-Al(Mn,Fe)Si phases varies with the holding time and temperature. For very long holdings, these compositions are closed to equilibrium values given by Thermo-Calc using the Saunders the database.
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