Thermal Analysis of the Mechanism and Kinetics Parameters of the Metastable Phases Precipitation in the Al-Mg-Si Alloy

In this experimental study, the mechanism and kinetic parameters of the metastable phases precipitation in the Al-Mg-Si alloy were determined thermally by differential scanning calorimetric (DSC) analysis. All samples were treated up to 550 degrees C at heating rates of 5, 10, 20 and 30 degrees C/min. The apparent activation energy (56.74 kJ / mol) and the Avrami exponent (0.99), were determined by DSC using the non-isothermal conditions with the Ozawa, Boswell and Kissinger methods. While those obtained under isothermal conditions with the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model, were 51.04 kJ/mol and 1.18 respectively. The activation energies values indicate that the formation of the metastable phases were mainly controlled by the migration of Mg and Si. The (n) values are characteristics of a plate growth after saturation of nucleation. The frequency factor (k(0)) calculated by the isothermal method was found to be 8.36x10(7) s(-1).