Analysis of the evolution of Mg₂Si precipitates during continuous cooling and subsequent re-heating of a 6061 aluminum alloy with differential scanning calorimetry and a simple model

In Al-Mg-Si alloys the presence of β-Mg2Si precipitates crucially affects strength and recrystallization during hot deformation and annealing. This work contributes to the understanding of the evolution of β-Mg2Si precipitates throughout a typical production process by investigating a continuous cooling and re-heating sequence with differential scanning calorimetry at varying rates. A simple model for nucleation and growth with improved numerical properties is presented and validated with the help of the calorimetric curves. The model, which is designed for future implementation in a finite element software, is shown to be very suitable for predicting the phase formation during cooling but limited for predicting the phase dissolution during re-heating.