In the last decade light materials have been studied thoroughly and used in components of pieces in the automobile, naval and aerospace industries. Their application makes possible mass reduce, load capacity increase, improvement in the mechanical properties when it is possible. Aluminium-magnesium alloys present good mechanical properties at moderate mechanical efforts (400 to 700 MPa) and good corrosion resistance. The alloys in study (Al-2Mg-0.6Zr and Al-2Mg-1Nb) were made by powder metallurgy (P/M) techniques, employing hot compactation and extrusion processes followed by cold work and thermal treatments. The analysis by SEM and TEM shows an evolution in the microstructure of precipitates with the increase of the time of thermal treatment, according to literature. The distribution of the precipitates in both alloys was observed and identified by EDS microanalysis (SEM and TEM).