Precipitation kinetics in supersaturated Al-2.0 at% Cu-1.0 at % Mg alloy

Abstract

In Al-2.0at%Cu-1.0at%Mg alloy, fine-scale precipitates that occur during aging have been investigated by using differential scanning calorimetry (DSC) to search for the phase transition temperatures (formation and dissolution of precipitates). The microhardness measurements (HV) are used to correlate between the developed reaction peaks in DSC and the observed peaks in the microhardness (HV). The scanning electron microscopy (SEM) is utilized to examine the surface microstructure of the precipitated phases and to confirm the obtained results. During the aging treatment the supersaturation is gradually reduced. The strength increases when fine coherent and/or semicoherent precipitates nucleate. The precipitation kinetics can be characterized by analyzing the DSC curves. The kinetics of the early stage precipitates were found to be controlled by the migration of Cu and Mg atoms in the matrix. Whereas, the later precipitates as S", S′ and S are controlled by diffusion of Mg and Cu in the alloy. © 2010 The Japan Institute of Metals.