Laser-based powder bed fusion of metals exhibit process-induced anisotropy and residual stresses, making post-manufacturing heat treatment occasionally beneficial. For AlSi10Mg, a T6 heat treatment (solution annealing, quenching, artificial aging) is recommended. Nevertheless, mechanical strength decreases as (1) the eutectic Si network dissolves, (2) the amount of dissolved Si in the Al grains decreases, and (3) the size of the silicon particles and aluminum crystals increases during solution annealing. This changes the mechanical characteristics directly or by influencing the formation of precipitation during the aging process. The success of solution annealing is affected by the annealing duration and the part’s temperature at the moment of quenching. Short annealing durations dissolve a sufficient amount of Si and Mg in the Al matrix. Therefore, both the annealing temperature’s holding duration and the heating process significantly impact the resulting microstructure. In this study, samples of different shape and size where subjected to a T6 heat treatment with different solution annealing temperatures and durations. The influence on mechanical properties after quenching and aging was investigated by hardness and tensile tests. Maximum strength is achieved by quenching promptly upon reaching the solution annealing temperature, while longer durations reduce strength as explained by the Larson-Miller parameter.