Precipitation kinetics of Si in aluminium alloys

Fernando Lasagni, Bernhard Mingler, Myriam Dumont, H.P. Degischer

The precipitation kinetics of Si in an Al¿1.7 wt.%Si alloy after different thermal treatments has been studied by means of transmission electron microscopy (TEM), dilatometry and differential scanning calorimetry (DSC). The results obtained are explained by a model based on simple nucleation and growth/dissolution laws and are compared with measured precipitate size distributions. The evolution of precipitates in water-quenched samples during linear heating depicts the exothermic formation of platelets and globular Si precipitates (200¿300 °C). The endothermal dissolution of Si platelets starts at lower temperatures than that of the globular precipitates. Coarsening and finally dissolution of globular precipitates is observed with increasing temperature. Samples slowly cooled from the solution treatment temperature present mostly globular precipitates, which are nucleated during cooling. Here, an exothermal effect related to the growth of Si precipitates increasing their volume fraction is observed at relatively high temperatures (350¿460 °C) during linear heating. The formed precipitates are stable up to 460 °C, where the modelled critical radius becomes bigger than most of the Si precipitates formed so far.

Physics of Nanostructured Materials
External organisation(s)
Technische Universität Wien, Université Paul-Cézanne Aix-Marseille III
Materials Science and Engineering A: Structural Materials: Properties, Microstructures and Processing
Publication date
Peer reviewed
Austrian Fields of Science 2012
103018 Materials physics
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