The impact of pre-shock loading on the precipitation reactions in an Al-Mg-Si alloy (AA6022) was studied by means of differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and hardness measurements. The samples were solutionized and quenched in water prior to subsequent shock-loading and aging treatment. The TEM and DSC results show that, while shock-loading prior to aging facilitated the precipitation of Q' and, no significant effect on beta" precipitates was observed. The hardness studies indicate that pre-shock loading strengthens the material by forming a high concentration of microstructural defects, however the resultant mechanical properties of the shocked sample are comparable to those without shock processing at the peak of aging. It was found that the rate of overaging is higher in shocked samples, which is in agreement with the DSC and TEM results. (c) 2006 Springer Science + Business Media, Inc.