Effect of the printing orientation on the yield surface and its evolution reflecting plastic pre-deformation of additively manufactured stainless steel 316L

Abstract

This study explores the influence of printing orientation on the yield surface characteristics and their evolution under plastic pre-deformation in additively manufactured (AM) stainless steel 316L produced via laser powder bed fusion (LPBF). Tubular specimens were fabricated in three orientations (XY, ZX, and Z) and subjected to multi-axial loading to experimentally determine initial and subsequent yield surfaces using a single-specimen probing approach. The yield surfaces were derived at two offset strain definitions (0.001% and 0.005%) and further analyzed after tensile pre-deformations of 0.35%, 0.5%, and 0.8%. Results revealed strong anisotropy in the AM specimens, with the Z-oriented samples displaying the lowest yield strength and most significant softening. In contrast, the XY and ZX orientations exhibited higher resistance to plastic deformation. The wrought SS316L showed superior mechanical performance. The evolution of yield surfaces highlighted the orientation-dependent hardening/softening mechanisms and directional stress redistribution. Electron backscatter diffraction (EBSD) analysis revealed that the microstructural anisotropy and grain morphology—particularly the presence of columnar grains in the Z-oriented samples—correlate strongly with the observed mechanical anisotropy and yield surface asymmetry.