Precipitation sequence in Al-Mg-Si-Sc-Zr alloys during isochronal agingWednesday (06.11.2019) 14:55 - 15:15 Part of:
6xxx-series Al alloys are the most commonly used alloys in the automotive industry as they have an appropriate balance of strength, corrosion resistance and formability. These alloys experience significant strengthening from the precipitation of the β’’ precipitates. One opportunity to achieve stronger 6xxx-series Al alloys, without affecting corrosion and formability, is the use of Sc. These strengthening benefits are obtained by the formation of the Al3Sc dispersoids. Prior studies report a detrimental impact from adding Sc to Al-Mg-Si alloys that is mainly due to a general lack of understanding of microstructural development in these alloys. Here we show, that combining conductivity, hardness and modelling allows for the prediction of the precipitation sequence in these alloys. To achieve this, an Al-Sc-Zr, Al-Mg-Si and an Al-Mg-Si-Sc-Zr alloy were prepared and solutionised. The evolution of conductivity and hardness during isochronal aging of these alloys is discussed in terms of solute depletion and precipitate formation. Theoretical modelling allows estimating the precipitation kinetics of the Mg-Si precipitates and Sc-Zr dispersoids during isochronal aging. These results can be used to design a suitable heat treatment for these alloys that allow for the formation of both fine Al3(Sc,Zr) dispersoids and fine MgSi precipitates.