Synchrotron radiation small-angle X-ray scattering study on reversion process of G.P. zones in Al-Zn binary alloys

The reversion process below the miscibility gap has been investigated for Al-Zn binary alloys by means of in-situ Synchrotron radiation small-angle X-ray scattering (SR-SAXS). In the present study, it was made clear that the structure change during the reversion below the miscibility gap was divided into two processes, i.e., the reversion process and the coarsening process. Also, in th reversion process there were two stages. The early stage of reversion was characterized by the decreasing solute concentration and a constant volume fraction of the zones. The later stage was characterized by the decreasing volume fraction and a constant solute concentration of the zones. Comparison with a model calculation based on two-phase Stephan problem suggested that the two-phase model could describe well the structure of the G.P. zone during the reversion below the miscibility gap as well as above it. (author)