Nucleation of equiaxed grains upon solidification of Laser powder bed fusion (L-PBF) processed alloys is of paramount importance especially in high-strength Al alloys to avoid hot cracking phenomena and to reach the expected performance.

This effect is usually achieved by adding Ti and B, to promote nucleation by TiB2 nanoparticles at the liquid stage, or by alloying the Al melt with elements able to promote the precipitation of Al3X-type phases having L12 structure. These latter precipitates are known to be very powerful nucleants for new grains upon solidification and can additionally promote significant strengthening by a proper post-process aging treatment.

The present contribution is particularly focussed on the mutual effect provided by the combined use of Zr, Sc and other elements in Al-Mg alloys specifically designed for L-PBF processing. Calphad-based simulation were first carried out to establish the expected solidification behaviour and the precipitation kinetics upon solid state treatments, considering different combination of the above elements.

In a following stage, some selected alloys were produced in the form of gas atomized powders and the corresponding alloys were tested for their printability and achievable microstructural and mechanical performance.

The general output of the research allows drawing useful information about the most appropriate design options for high-strength Al alloys developed for L-PBF processes, considering aspects related to cost, sustainability, performances.