Laser-based powder bed fusion additive manufacturing and mechanical characterization of 316 L stainless steel auxetic lattice structures

The mechanical mismatch between metallic implants and bone tissue is a well-recognized challenge in load-bearing biomedical applications and is commonly associated with stress shielding effects. Architected cellular materials, and in particular auxetic lattice structures, offer a promising route to tailor mechanical response through geometry rather than material substitution alone. However, the mechanical behavior of metallic auxetic lattices fabricated under realistic additive manufacturing conditions, especially their static and fatigue performance, remains insufficiently understood. In this study, the mechanical response of additively manufactured metallic auxetic lattice structures is experimentally investigated using stainless steel 316 L as a well-characterized reference material. Re-entrant auxetic lattice geometries were fabricated via laser-based powder bed fusion (L-PBF) and subjected to controlled post-processing heat treatments. Static tensile and compressive tests, together with compression fatigue experiments, were conducted to evaluate stiffness modulation, strength, deformation stability, and fatigue durability. Finite element analysis was employed as a complementary tool to support interpretation of observations and replicate manufacturing effects, i.e., shape deviation, along the fabrication process chain including heat treatment. The mechanical characterization results demonstrate that auxetic lattice architecture enables substantial stiffness reduction relative to bulk material while maintaining load-bearing capability. Heat-treated specimens exhibited improved ductility and significantly enhanced fatigue resistance compared to as-built structures, highlighting the critical role of post-processing in governing long-term mechanical performance. At the same time, the findings reveal inherent trade-offs between stiffness reduction and strength in highly porous auxetic lattices. Overall, this work provides experimentally grounded insights into the structure–property relationships of metallic auxetic lattices manufactured by L-PBF. By clarifying the mechanical mechanisms that control stiffness, strength, and fatigue response, the study establishes a mechanical foundation for future investigations involving optimized geometries, advanced materials, and application-specific requirements, including orthopedic implant design.