EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

During heating of Al alloys, typically a sequence of precipitation and dissolution reactions occurs and the single reactions superimpose. Differential scanning calorimetry (DSC) is one common technique to analyse the kinetic development of precipitation and dissolution in Al alloys, but the superposition of the exothermal precipitation and endothermal dissolution reactions complicates the DSC signal interpretation, as DSC measures the sum of any heat effect. Synchrotron wide-angle X-ray scattering (WAXS) allows the kinetic development of phase transformations to be obtained and can support the separation of superimposed DSC signals. WAXS results from this work offer a new approach to separate part of the superimposed reactions and their kinetic development for the equilibrium phases β-Mg2Si in EN AW 6082 and η-Mg(Zn,Cu,Al)2 in EN AW 7150. Comparing DSC and WAXS results confirms serious overlap issues. Common DSC evaluation methods using zero crossing between endothermal and exothermal heat flow or peak positions are misleading regarding individual reaction start and finish temperatures as well as regarding reaction intensities.