Extrusion based metal additive manufacturing of lattice-cored solid shell structures for lightweight applications

Abstract

AbstractAutomotive, healthcare, and aerospace industries need lightweight metallic structures. Traditional manufacturing technologies struggle to create complicated geometries for such applications. Such demands have driven metal additive manufacturing (AM) techniques like laser powder bed fusion (LPBF) and direct energy deposition (DED). Lightweight components frequently require a solid outer shell with somewhat hollow inside, which is difficult to fabricate. Lattice infill patterns reduce material usage, while powder-bed AM techniques trap loose powder in voids, adding weight. In contrast, extrusion-based metal AM (FDMet) allows closed-shell lattice designs without powder entrapment. FDMet was used to produce lattice-cored solid-shell 316L stainless steel components with gyroid, concentric, cubic subdivision, triangle, and zigzag infill structures (20% density). Evaluation of tensile and three-point bending behavior revealed that the zigzag infill had the lowest ultimate bending stress (263.08 ± 24.70 MPa) and the highest ultimate tensile stress (154 ± 17.47 MPa). In contrast, the concentric infill had the highest ultimate bending stress (366.02 ± 20.62 MPa) and the lowest ultimate tensile strength (75 ± 10.845 MPa). SEM fracture analysis and infill imaging correlated mechanical response with internal geometry. FDMet was evaluated against LPBF and wrought 316L stainless steel using X-ray diffraction (XRD), Electron Backscatter Diffraction (EBSD), tensile (solid), nanoindentation hardness, and scratch resistance testing. FDMet parts showed the highest porosity (approx. 1.71%) due to voids from layer extrusion and binder removal, while LPBF samples had the lowest porosity (approx. 0.044%) due to complete powder melting and consolidation. Solid FDMet components had the lowest ultimate tensile strength (approx. 660 MPa) while wrought 316L had the highest (approx. 800 Mpa). FDMet components had the lowest nanoindentation hardness (5.95 ± 0.17 GPa) while wrought 316L had the greatest (6.32 ± 0.38 GPa). FDMet components have equivalent properties compared to other methods despite lower tensile stress, hardness and increased porosity. FDMet samples showed lower residual stress than LPBF and wrought samples due to reduced stored strain (kernel average misorientation). © 2026 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.