Influence of lithium on the kinetics of phase transformation in 7000 series aluminum alloy by SAXS investigation

To understand deeply the influence of lithium on 7000 series aluminum alloys, to obtain the Li-containing high strength alloys with good performance, the 7000 series Li-containing alloys are studied. The phase transformation kinetietics of the 7000 series Li-containing alloys containing lithium is investigated in comparison with Li-free 7000 series alloys by small angel X-ray scattering (SAXS) experimental measurements. The parameters for precipitate mean size and volume fraction are obtained by SAXS theory, and the activation energy for three stages is further obtained on the basis of the above information, including nucleus, growing and coarsening. The results show that as compared with Li-free alloys, the precipitation process of growing and coarsening is slower and nucleus activation energy is smaller, but the activation energy of growing and coarsening is larger in Li-containing alloys. It suggests that nucleus formation is easier, but the precipitation coruse of growing and coarsening is more difficult in Li-containing alloys than in Li-free alloys.