Fabrication strategy and mechanical behavior of large-size 316L stainless steel lattice structures via directed energy deposition-arc

The demand for lightweight high-performance structures in various industries has driven the development of advanced manufacturing techniques such as additive manufacturing (AM). Lattice structures, in particular, offer unique combinations of properties, but present challenges in manufacturing owing to their complex geometries. Traditional manufacturing methods struggle to produce large-scale lattice structures with controlled porosities and complex topologies. Additionally, ensuring the mechanical integrity of the node connections in these structures is a significant challenge. Directed energy deposition-arc (DED-Arc) method offers a promising solution because of its high deposition efficiency and scalability. This study proposes a gas tungsten arc welding (GTAW)-based DED-Arc strategy to fabricate body-centered cubic (BCC) lattice structures with optimized nodal connections. Microstructural analysis revealed that coarse equiaxed grains were formed at the nodes owing to the elevated heat input, which reduced the tensile strength by 15% compared with the rod elements. Compression tests demonstrated an equivalent yield strength of 4.6 ± 0.3 MPa and elastic modulus of 187.6 ± 18.3 MPa for 2 × 2 BCC units, and three-point bending tests identified panel-strut interfacial failures (peak load: 50.5–54.5 kN). The experimental results were validated against computational simulations, which demonstrated a strong agreement between the predictions and the experimental observations. Thus, the proposed GTAW-based DED-Arc method is reliable for producing BCC lattice structures; however, further optimization is required to improve the mechanical properties and bonding at the node connections. This study provides valuable insights into the manufacturing process and mechanical behavior of lattice structures, thereby guiding future improvements.