Quantitative study of precipitates in an Al–Zn–Mg–Cu alloy aged with various typical tempers

The present work gives a quantitative study on the nanoscale precipitates in an Al–Zn–Mg–Cu aluminum alloy (AA7150) when subjected to different aging tempers, i.e., T6, T79, T76, T74, T73 and RRA, by combining synchrotron-based small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) techniques. Based on the TEM observations, the distributions of volume fraction and number density as a function of precipitate size are extracted from SAXS data through model fitting. The results show that with the deepening of aging degree, the size and number density of precipitates are two key factors for tailoring the mechanical strength of the alloy, whereas the increasing volume fraction of precipitates contributes to the increasing electrical conductivity. The results also show that as the degree of over-aging deepens, the precipitate size distribution interval becomes broader.