A small-angle X-ray scattering study of late-stage delta ' 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 deve loped to reconstruct the free-form particle size distribution of precipitat es by including the interparticle interference effect. In this gaper, the k nown indirect Fourier transform method (ITM) is extended to include the har d-sphere (HS) model which considers the interaction between the precipitate s. This method is tested by analyzing simulated SAXS data and shows a bette r agreement than other similar studies. Then this modified method is applie d to analyze several experimental SAXS data from delta' (Al3Li particles) p recipitation in Al-7.9at% Li alloys aged at various conditions, The variati on of average radii with aging time was found to follow the kinetic power l aw. The SAXS results are used to investigate the kinetic model of the delta ' coarsening (Ostwald ripening) with volume fraction effect. When comparing both experimentally obtained asymptotic size distributions of delta' parti cles 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 experimen tal results. The dynamic scaling behavior of this phase separation is also investigated. (C) 1999 Elsevier Science B.V. All rights reserved.