Chernyshova, PGuraya, TMartinez-Amesti, AAndonegi, HSingamneni, SChen, ZW2023-05-242023-05-242023-04-23Advanced Engineering Materials, ISSN: 1438-1656 (Print); 1527-2648 (Online), Wiley. doi: 10.1002/adem.2023001351438-16561527-2648https://hdl.handle.net/10292/16171Scalmalloy is an Al–Mg alloy with additions of Sc and Zr originally developed as a high-strength aluminum alloy with σ0.2 ≥ 450 MPa for aerospace industry. It is now well understood that the alloy is amendable for processing by laser powder bed fusion (LPBF). However, the mechanism of formation of the equiaxed-columnar bimodal grain structure during LPBF is not ascertained yet, fully. Herein, this gap is addressed with special focus on the distributions of critical elements such as Sc and various particles that form during LBPF. It is found that strong and weak segregation of Mg and Sc, respectively, occurs in the final solidification areas of the fine- and equiaxed-grain regions. The coarser and columnar grain regions show weak segregation of Mg and no Sc segregation. A priori knowledge on the Al–Sc eutectic reaction, its dependence on cooling rates, and the well-known thermal and solidification conditions related to the track location during LPBF is used to ascertain the mechanism of formation of the bimodal grain structure. The mechanism suggested is substantiated by the location-dependent elemental distributions and the various particles that are observed.http://creativecommons.org/licenses/by/4.0/4014 Manufacturing Engineering40 Engineering0912 Materials EngineeringMaterials4005 Civil engineering4016 Materials engineering4017 Mechanical engineeringJournal ArticleOpenAccess10.1002/adem.202300135