A small-angle X-ray scattering study of late-stage δ′ precipitation in Al-7.9%Li alloy for growth kinetics and dynamic scaling

A modified method for small-angle X-ray scattering (SAXS) analysis was developed to reconstruct the free-form particle size distribution of precipitates by including the interparticle interference effect. In this paper, the known indirect Fourier transform method (ITM) is extended to include the hard-sphere (HS) model which considers the interaction between the precipitates. This method is tested by analyzing simulated SAXS data and shows a better agreement than other similar studies. Then this modified method is applied to analyze several experimental SAXS data from δ′ (Al 3 Li particles) precipitation in Al-7.9at%Li alloys aged at various conditions. The variation of average radii with aging time was found to follow the kinetic power law. The SAXS results are used to investigate the kinetic model of the δ′ coarsening (Ostwald ripening) with volume fraction effect. When comparing both experimentally obtained asymptotic size distributions of δ′ particles with those predicted by the kinetic theories, the MLSW theory is found to be in better agreement with the experimental results. This work gives a more clear interpretation of the coarsening mechanism than other experimental results. The dynamic scaling behavior of this phase separation is also investigated.