Simulation of the effect of composition on the precipitation in 6xxx Al alloys during continuous-heating DSC

The precipitation behaviour of Al-Mg-Si alloys has been studied by differential scanning calorimetry (DSC) and by thermo-kinetic modelling. Three industrial alloys with different main solute contents, namely Mg, Si, Cu are used. Main aspect is given to the different Mg/Si ratios of the investigated alloys. Observed exothermic and endothermic peaks, accompanying the formation or dissolution of precipitates, are attributed to the formation or dissolution of individual phases, a procedure, which becomes rather involved if precipitation peaks of phases overlap. In the present paper, we propose a combination of experimental DSC analysis and computer simulation of precipitation kinetics to overcome this problem. By an iterative thermo-kinetic optimization of the simulation parameters and comparison with the heat flow evolution of the experiment, a unique picture of the complex precipitation process for different Mg/Si ratios is obtained. Exemplarily, experimental heat flow curves of various 6xxx Al alloys are unravelled and compared to the heat flow evaluated with thermo-kinetic computer simulations.