Anisotropic tensile properties and microstructure of SS316LSi fabricated using wire-based laser directed energy deposition

This paper investigates the anisotropic mechanical properties and microstructures of two austenitic stainless steel 316LSi vertical wall components fabricated using laser wire-directed energy deposition (LW-DED). ASTM standard tensile specimens were extracted from different locations of these twin walls. The specimens’ mechanical properties in longitudinal and transverse orientations relative to the build direction were assessed under uniaxial tension. A select number of speciments were subjected to heat treatment at 1100 ^oC to evaluate its impact on anisotropy, ultimate strength, and ductility. Digital image correlation (DIC) was employed to analyze strain field evolution in two representative horizontal and vertical specimens. Fractured surfaces were examined using scanning electron microscopy. The results showed an average ultimate tensile strength of 550 MPa in both directions, with a maximum strength of 680 MPa in specimens from the median location. This variation was attributed to residual stress differences across the printed wall, as confirmed by finite element analysis. The average elongations were 25 % and 35 % for vertically and horizontally extracted specimens, respectively. Heat treatment enhanced ductility by 15–20 % for both categories due to grain structure coarsening. The anisotropy in ductility was primarily because of the differences in columnar grain orientation with the coarser grains aligned with the tension direction in horizontally extracted specimens. This alignment facilitated damage accumulation, leading to tensile fracture. This study provides insights into the anisotropic behavior of LW-DED SS316LSi components and the influence of heat treatment on tensile properties.