Abstract: Hot torsion tests were carried out on an aluminium alloy containing 0.7%Mg-0.97%Si. The flow curves at 500/530/560℃ and at strain rates ranging between 0.05 and 1.5 S-1were measured. The influence of the microstructural changes during and after hot working on the isothermal precipitation kinetics of Mg2 Si and on the subsequent aging behavior of the alloy quenched directly after hot deformation was investigated. It has been found that the age-hardening ability and the aging time to peak hardness are related to holding time after hot deformation to quenching. If the holding time is within is, the peak hardness is 25% higher and aging time is an order of magnitude shorter for the sample quenched directly after hot deformation than for the sample quenched conventionally. In comparison with the aging microstructures of the sample quenched conventionally, the aging microstructures of the sample quenched immediately after hot deformation are characterized by the existence of recovery substructures and finer and more dispersive precipitates.