Study of Precipitation Hardening in Two Al-Mg-Si Alloys with and without Copper and Excess Silicon Using Kissinger and Boswell Methods

Abstract

The precipitation of two 6xxx (Al-Mg-Si) alloys with and without copper (Cu) and excess silicon (Si) has been investigated by using the differential scanning calorimetry (DSC), transmission electron microscopic (TEM) and X ray diffraction (XRD) analysis. The analysis of the DSC curves found that the excess Si accelerate the precipitation. The values of activation energies for each peak of DSC curves were determined by using Kissinger–Akahira–Sunose (KAS) and Boswell isoconversional methods. The alloy which has an excess Si and copper require larger activation energy for precipitation despite the acceleration of the precipitation by the excess Si. TEM observation result shows there is smaller size and higher density of precipitate in excess Si alloy than those of excess-free.

In situ high-energy X-ray diffraction of precipitation and dissolution reactions during heating of Al alloys

“…This is even more doubtful if the DSC peaks are used for the determination of activation energies for the precipitation of specific phases, such as in many works, (e.g. [7][8][9][10][11][12][13][14][15]), for instance, by applying evaluation methods like the Kissinger method [16].…”