Differential scanning calorimetry (DSC) was used to study the precipitation kinetics of metastable phases in an Al6061 alloy and a 20 vol % alumina particle reinforced Al6061 composite. The thermal effects in the DSC traces were analysed quantitatively. The kinetic parameters for the phase transformations in the Al6061 alloy and composite were calculated using the varying heating rate method and the Kissinger approach. It was found that the overall age-hardening sequence of the Al6061 alloy did not change due to the addition of Al2O3 particles, but the volume fractions of the various phases and the precipitation kinetics of some of the phases were modified. The precipitation transformations of the metastable phases in both the Al6061 and the composite obey an n-order kinetic model. © 1998 Kluwer Academic Publishers