In this presentation, a novel in-situ heat treatment of a Sc-modified Aluminium alloy (Scalmalloy) is proposed by exploiting the thermal peculiarities of the laser powder bed fusion process, giving insights into the process-microstructure-property relationship. The thermal history was simulated a multi-scale finite element simulation to adjust the heating unit to the proper processing window. Although on macro-level the same bi-modal microstructure is maintained when processing the material with an in-situ heat treatment, the precipitation structure on nano-scale is altered significantly by the formation of solute clusters, as found by high-resolution analysis. The formation of these solute clusters can be traced back to the up-quenching concept, combining the elevated temperatures and the excess vacancies produced during the cyclic reheating of the material by the fusion process zone. As a result, mechanical testing confirmed the same strength values in the directly manufactured as-built state of the in-situ heat treated specimens as their peak aged counterparts without in-situ heat treatment.