Long-term correlations distinguish coarsening mechanisms in alloys

We determine long-term correlations in the time series of fluctuating x-ray speckle intensities. A fluctuation analysis of small angle x-ray scattering data of the two phase-separating alloys Al-6 at. %Ag and Al-9 at. %Zn at late stages of phase separation reveals long-term correlations that are dramatically different for the two systems. From a comparison with recent Monte Carlo simulations we conclude that two different coarsening mechanisms are predominant in the two alloys—coarsening either by diffusion of single atoms or by movement of whole precipitates.