AA2024 and 7010 friction stir welds are examined in order to determine the precipitation state in the various zones of the welds. Direct observations of the precipitates are made using Field Emission Gun Scanning Electron Microscopy and Transmission Electron Microscopy. The solid solution and GP zone effect is evaluated through local conductivity measurements. Differential Scanning Calorimetry on samples taken from the weld allows characterizing further the precipitation. Hardness and tensile testing contribute to the description of the weld.