Polycrystalline specimens of Al–1% Mg2Si (0.2% excess Si), annealed at temperatures between 443 and 650 K after solution treatment and water quench show an internal friction peak at 480 K (1 Hz). It is proposed as a Si precipitate grain boundary peak. In macrocrystals, another peak appears during the first cooling from 620 K. It is located at 465 K (1 Hz), but under long aging it shifts to higher temperatures and increases its height. From this and other characteristics, it is concluded that this peak originates in a relaxation mechanism in which dislocations as well as precipitates in volume could participate. Des echantillons polycristalline d'Al–1% Mg2Si (0,2% de Si en exces), qui ont ete solubilises, trempes a l'eau et recuits entre 443 et 650 K, donnent lieu a l'apparition d'un pic de frottement interieur a 480 K (1 Hz), propose comme un pic de joint de grains avec du Si precipite. Dans des macrocristaux, on observe un autre pic a 465 K (1 Hz) durant le premier refroidissement des 620 K, mais quand on fait des longs recuits, il se deplace vers des hautes temperatures avec un accroissement du maximum. On conclue que ce pic est dǔ a un mecanisme de relaxation concernant les dislocations et les precipites en volume.