Resonant ultrasound spectroscopy (RUS) and pulse-echo (PE) measurements were used to evaluate the degree of elastic anisotropy in 316L stainless steel manufactured by selective laser melting (SLM). During fabrication, the laser beam was perpendicular to the sample’s top surface, executing in-plane single-pass parallel tracks with a 90 deg rotation between adjacent layers. Manufactured over a wide range of laser power (40–100 W) and laser speed (600–1200 mm/s), the set allows for an extensive database of samples with microstructure and elastic properties dependent on manufacturing parameters. The RUS analysis exhibits varying degrees of success depending on the degree of texturing within the polycrystalline sample and the assumed symmetry. As the volumetric energy density (VED) decreases, the assumption of volumetric isotropy (ideal polycrystal) vs. transverse isotropy in the RUS analysis produces results that are increasingly closer. At the highest VED, the RUS fits have large errors under either symmetry assumption. The through-thickness PE measurements yielding a deterministic value for c33 (3 ≡ build-direction) provided a reference for the probabilistic RUS analysis. Characterizing variations and directional dependence in the elastic properties of SLM materials is key for their future implementation.
Hayward et al. (Wed,) studied this question.