Influence of Fe contamination on the processability and mechanical properties of silicon fabricated by Laser Powder Bed Fusion

– Silicon, a key material in electronics, is traditionally processed through subtractive methods that limit geometric complexity. Laser Powder Bed Fusion (L-PBF), an Additive Manufacturing (AM) technique, offers a pathway to overcome this limitation by enabling the production of three-dimensional silicon structures. However, brittleness, cracking, and residual stress remain major challenges. Contamination is another critical factor, as metallic impurities such as iron are almost unavoidable in commercial silicon powders and can strongly influence processability and microstructure evolution. The present study investigates the L-PBF processing of silicon powder under varied volumetric energy densities. Samples were fabricated through a systematic optimization procedure, and their microstructures were analyzed to evaluate the role of iron-based phases originating from both the substrate and the feedstock. Volumetric energy densities (VED) within the range of 200-400 J/mm 3 promoted the formation of fine, dispersed FeSi 2 networks, which were associated with higher fracture toughness values (K IC = 1.098-1.164 MPa·√m at 200 J/mm 3 and up to 1.048 MPa·√m at the top region for 400 J/mm 3 ) and more isotropic mechanical responses. The presence of Fe-silicides appeared to correlate with enhanced local densification by lowering the melting point of the Si-Fe system and promoting melt coalescence. In contrast, excessive energy input increased Fe dilution, leading to cracking, porosity, and coarse, brittle FeSi 2 networks. These findings suggest a complex interaction of iron-based impurities during L-PBF of silicon (influencing densification mechanisms while becoming a major embrittlement agent at higher concentrations), providing insight into impurity-driven microstructural evolution and process stability.