Small-angle scattering from a commercial Al-Li alloy

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Abstract
Small-angle X-ray scattering measurements are reported for a commercial A1-2 wt% Li alloy solution treated at 520°C and thermally treated for several times at several temperatures. Data have been analysed by means of a method previously reported which, as it incorporates interparticle interference effects, reproduces the scattering intensities of the samples studied. During the thermal treatment the precipitate volume fraction remains constant, while the number density decreases with increasing time at the various temperatures. The scattering observations from the earliest time treatments are consistent with a precipitate-coarsening mechanism in which phase separation is complete and the average particle volume grows linearly with time. The precipitate and matrix concentrations are determined from the analysis of the scattering curves and indicate considerable non-stoichiometry in the precipitate. The interparticle spacing and particle size are scaled in a fixed ratio to one another in the course of thermal treatment which is consistent with the evolution of a self-similar structure.