Study of the developed precipitates in Al-0.63Mg-0.37Si-0.5Cu (wt.%) alloy by using DSC and TEM techniques

Heat treatable Al-Mg-Si containing Cu alloys can be strengthened by the precipitation of the nano-scale metastable precipitates. In order to follow the precipitation sequence in balanced Al-1 mass%Mg2Si containing 0.5 mass%Cu during continuous heating, differential scanning calorimetry (DSC) was performed. Analysis of non-isothermal DSC scans at various heating rates were carried out to evaluate the overall activation energies associated with the precipitation processes and, therefore, the mechanism of the developed precipitates has been characterized. The most important developed precipitates that assist the strength of the alloy are random, Q′ and β′ precipitates. According to the obtained activation energies, the kinetics of the evolved Q′-precipitates could be controlled by the diffusion of Mg, Si and Cu in the crystal lattice of the alloy. Both conventional and high resolution transmission electron microscopy (HRTEM) were utilized to confirm the obtained results.