DECOMPOSITION PROCESSES IN AN Al-5% Zn-1% Mg ALLOY - 3. REVERSION OF GP-ZONES.

The dissolution of GP-zones during various reversion treatments was studied by isothermal microcalorimetry and thermal analysis (DSC). During reversion, the formation of high-temperature precipitates on vacancy-rich clusters (VRC) and GP-zones was generally found, which would influence the kinetics of subsequent aging. A special reversion treatment could be determined which dissolved totally a given GP-zone distribution and erased all ″memory″ of the previous aging. Furthermore, it is shown that the concentration of mobile excess vacancies and VRC-nuclei is reduced by reversion.