Abstract:
In this present research work, we have investigated the precipitation of two
Al-Mg-Si alloys with and without Cu and excess Si by using the differential scanning
calorimetry (DSC), transmission electron microscopic (TEM) and Vickers hardness
measurement. The analysis of the DSC curves found that the excess Si accelerate the
precipitation and the alloy contain the excess and small addition of copper has higher
aging-hardness than that of free alloy (without excess Si and Cu) at the same heat
treatment condition. TEM observation result shows there is smaller size and higher
number density of precipitate in excess Si-bearing alloy than those of excess-free. Also,
the activation energy for each peak of DSC curves (exothermic and endothermic
reactions) was calculated. The alloys with an excess Si require larger activation energy for
precipitation despite the acceleration of the precipitation by the excess Si
