Calorimetric studies and kinetic parameters of solid state reactions in 7017 Al-Zn-Mg alloy

Abstract

Differential scanning calorimetric (DSC) studies have been carried out at different heating rates to examine the solid state reactions in a 7017 Al-Zn-Mg alloy of water-quenched (WQ) state and artificial aged tempers. All the exothermic and endothermic peaks of the thermograms indicating the solid state reaction sequence have been identified and discussed. The shifting of peak temperatures of all the reactions to higher temperatures with increasing heating rates suggests that the reactions are thermally activated and kinetically controlled. The variations of hardness with aging time at an artificial aging temperature have also been studied to obtain the under-, peak- and over aged tempers. The fraction of transformation (Y), the rate of transformation (dY/dt), the transformation function f(Y) and the kinetic parameters such as activation energy (Q) and frequency factor (k0) of the solid state reactions in the alloy have been determined by analyzing the DSC data i.e. heat flow involved with the corresponding DSC peaks. It has been found that the kinetic parameters of the solid state reactions are in good agreement with the published data.