Abstract：Most existing isotropic metamaterial designs assume that the base material possesses isotropic symmetry. However, 316L steel produced by selective laser melting (SLM) typically exhibits mechanical anisotropy, which strongly depends on the manufacturing process and parameters. The limited experimental studies currently available are insufficient to fully reveal the elastic symmetry of 316L steel under different scanning strategies, and the quantitative impact of varying laser powers on Young's modulus remains unknown. In this study, ultrasonic resonance experiments were conducted to characterize the elastic constants of 316L steel under two typical laser scanning strategies (parallel and orthogonal scanning) and two laser power levels (214.2W and 274.2W). The results indicate that under the orthogonal scanning strategy, the symmetry of the steel degraded to transverse isotropy at a power of 214.2W, while the material remained orthotropic at a power of 274.2W, indicating that transverse isotropy results from specific laser power. Compared to orthogonal scanning, 316L steel produced using parallel scanning exhibited stronger anisotropy. Within the range of laser powers investigated, Young's modulus was found to be insensitive to power variations. Based on the experimentally obtained elastic constants and finite element simulations, we optimized the elastic isotropy of three types of truss metamaterials: FCC-BCC, SC-OT, and SC-OT-BCC, achieving shape control by adjusting rod dimensions. The optimization results showed that isotropic metamaterials made from SLM 316L steel and cast 316L steel possess nearly identical elastic properties. From an application perspective, this research offers feasible solutions to overcome the technical challenges of producing isotropic metamaterials using SLM additive manufacturing.
2025, Vol. 46 
