PRECIPITATION STAGES IN Al-Ag ALLOYS DETERMINED BY THE EVOLUTION OF THE INTERNAL FRICTION SPECTRUM

Abstract
The evolution of the internal friction spectrum during precipitation in Al-Ag alloys is characterized by the appearance of three atomic relaxation peaks and an evolution of the background due to the GP-zones evolution and to the precipitation hardening phenomena. Two of these peaks are Zener peaks due to the quenched solid solution and to the partially reverted one respectively, when the GP-zones are destabilized by the appearance of new metastable precipitates, the γ'' precipitates. The third peak is due to atomic relaxations inside the γ phase precipitates (γ' and γ). Its thermodynamical characteristics show that the γ'' precipitates are different from the γ' precipitates.