Precipitation kinetics in Al–Zn–Mg commercial alloys

The precipitation kinetics of two commercial Al–Zn–Mg alloys (7005 and 7012) was studied by using different experimental techniques. The precipitation sequence was previously investigated by means of positron annihilation lifetime spectroscopy (PALS) and Vickers microhardness. The results were correlated with quantitative information obtained by high resolution and conventional transmission electron microscopy (HREM and CTEM) and small-angle X-ray scattering (SAXS). Special attention was kept on the study of the microstructural evolution during the early stages of artificial aging. The results are discussed in terms of the formation, growth and partial dissolution of solute clusters or Guinier–Preston zones, and nucleation and growth of η′ precipitates.