A detailed in situ SAXS investigation is presented on the phase separation process in a commercial aluminum-lithium alloy. Taking advantage of conventional and synchrotron X-ray sources, it has been possible to probe both slow and fast kinetics. Both early and late stages of demixing are probed in a range of different temperatures between 75 and 200degreesC. The corresponding SAXS data are interpreted in terms of the currently accepted theories. The large temperature range covered in these measurements allows obtaining information on activated processes occurring in these materials.