Modeling the effect of Al3Sc precipitates on the yield stress and work hardening of an Al-Mg-Sc alloy

The yield stress and work hardening behaviour of precipitation hardening alloys is directly related to the nature of the interaction between mobile dislocations and precipitates. In commercial systems such as aluminium alloys, the understanding of this problem is complicated by the overlap between various mechanisms and the interplay between the volume fraction and size of precipitates and the residual solid solution content. In this study a model Al-2.8 wt.% Mg-0.16 wt.% Sc alloy has been chosen for examination since precipitation involves simple spherical precipitates, the absence of metastable phases and the solid solution effect is dominated by the magnesium content. Using a previously development precipitation model, it has been possible to develop an integrated yield stress/work hardening model in which the shearable/non-shearable transition and the size distribution of precipitates are explicitly accounted for. The agreement between the model and the experiments is excellent and the shearable/non-shearable transition radius is consistent with experimental observations.