The aging processes in Al-Mg-Si alloys have been studied by using differential scanning calorimetry (DSC), microhardness measurements (HV) and X-ray diffraction (XRD). Five processes have been detected by the DSC curves and HV behaviour. In the DSC curves, four exothermic and one endothermic reactions are developed. The sequence of processes are Guinier-Preston (G.P.) zones, dissolution of the G.P. zones, intermediate precipitation of W'-phase, precipitation of W -phase and precipitation of the stable b'-phase + Si particles. The activation energies associated with the processes have been determined by using Kissinger method. Consequently, the nucleation mechanism of the precipitates can be explained. These phases are confirmed by XRD analysis.

The fine-scale precipitates, that occurs during aging, the supersaturated Al–1.0 at.% Mg–x at.% Si (x = 0.6, 1.0 and 1.6) alloys have been investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The strength of the alloys increases as a high density of very fine β″ coherent and β′ semicoherent precipitates nucleate. The precipitates compositions have been determined by analyzing the X-ray diffraction (XRD) charts, by using Scherrer equation. The obtained results showed that the β″ and β′ precipitates size lies in the nanometer range (from 5 nm to 32 nm). In addition, increasing Si concentration has exhibited an increase in the density of the precipitates, which fortifies the physical properties.