Friction stir welding on aluminum alloy is seen as an alternative solution to riveting 2024 and 7075 aluminum alloys pieces in order to lighten aircraft structure. On these alloys, mechanical properties are linked to structural hardening due to solid state precipitation. A coupling approach is proposed in order to manage the precipitates distribution evolution taking place during the process and predict final properties. At macro-scale, a model is used to get the thermal evolution in the different parts of the welded zone. At micro-scale, a time-efficient precipitation simulation is developed based on a reliable thermodynamic description. A particle size distribution approach (PSD) is proposed to predict the nucleation, growth, dissolution and coarsening of stable and metastable phases. An accurate yield strength model is applied on the final distribution. Calibration is performed on differential scanning calorimetry studies (DSC), hardening test and tensile tests for both isothermal, non-isothermal and weld samples.