Experimental and modelling assessment of precipitation kinetics in an Al-Li-Mg alloy
Résumé
The precipitation behaviour in an Al-5 wt.% Mg-1.8 wt.% Li alloy has been systematically investigated for both isothermal and non-isothermal heat treatments, using atom probe tomography, transmission electron microscopy and in situ small-angle X-ray scattering. In the investigated temperature range, the delta' phase is shown to form, with a Mg content similar to that of the alloy, and a Li content of 18.5 at.%. The quantitative data on isothermal and non-isothermal kinetics from the in situ experiments are compared to the outcome of a precipitation class model adapted to the case of high volume fractions. The model parameters suggest that the main effect of Mg on the precipitation of the delta' phase in Al is to lower the solubility of Li in the alpha-Al solid solution, with little effect on the interfacial energy of the precipitates or on the Li diffusivity in Al. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved