A model for the thermodynamics of and strengthening due to co-clusters in Al-Mg-Si based alloys

摘要

An expanded model for the thermodynamics of co-clusters and their strengthening is presented, and the model is applied to predict co-cluster formation and strengthening in Al-Mg-Si alloys. The models are tested against data on a wide range of Al-Mg-Si alloys aged at room temperature. The strengthening due to co-clusters is predicted well. The formation of the co-clusters is studied in an Al-0.5at%Mg-1at%Si alloy using three-dimensional atom probe analysis. The results correspond well with the model. It is shown that in general, (short-range) order strengthening due to co-clusters will be the main strengthening mechanism in these alloys. Apart from the co-clusters, Si clusters also form, but due to their low enthalpy of formation, they contribute little to the strength.