Anisotropy in Young's modulus of thick – walled 316LSi Wire Arc Additive Manufacturing (WAAM) deposits

This study investigates elastic anisotropy in thick-walled 316LSi stainless steel deposits fabricated by Wire Arc Additive Manufacturing (WAAM). Four deposition conditions were evaluated by varying heat input (10 and 15 kJ/in.) and interpass temperature (121 and 399 °C), while maintaining a consistent alternating parallel toolpath strategy with 45% bead overlap. Optical metallography revealed that this tool path promoted cyclic partial remelting and produced a distinct periodic, wavy columnar grain morphology. Electron Backscatter Diffraction (EBSD) indicated corresponding crystallographic texture tendencies, with <100> alignment along the deposition direction (X-axis) and <111> alignment along the transverse direction (Y-axis). Since <111> is the stiffest and <100> is the most compliant crystallographic direction in FCC 316L/316LSi, these texture tendencies provide a mechanistic basis for the observed macroscopic elastic anisotropy. Room-temperature tensile testing showed a consistent orientation-dependent elastic response across all four processing conditions, with E Y > E X , while the Z-oriented specimens tested for the HH and HL conditions exhibited intermediate modulus values. Temperature-dependent resonant frequency and damping analysis (RFDA) measurements of the HL condition independently reproduced the E Y > E Z > E X directional stiffness hierarchy from 23 °C to 400 °C. The lowest Young’s modulus values were consistently measured along the deposition direction (X-axis: 146 to 150 GPa), while the highest values were observed along the transverse direction (Y-axis: 187 to 197 GPa). Overall, the observed elastic anisotropy was primarily associated with the toolpath-induced microstructure and crystallographic texture, while variations in heat input and interpass temperature had comparatively little influence within the processing window studied.