Anisotropic compression behavior of 316 L stainless steel at room and cryogenic temperatures: The influence of twinning and transformation mechanisms

Abstract

This study investigates the microstructural evolution and deformation behavior of 316 L stainless steel (SS) fabricated by direct energy deposition under compressive loading at room temperature (RT) and cryogenic temperature (CT), along the scanning (SD) and transverse (TD) directions. Electron backscatter diffraction, transmission electron microscopy, and electron channeling contrast imaging, combined with dislocation-based crystal plasticity simulations, were employed. The as-fabricated microstructure exhibited columnar grains with cellular substructures, and δ-ferrite at cell boundaries enriched in Cr and Mo. At RT, SD samples deformed via dislocation glide and twinning in [001]-oriented grains, gradually reorienting toward the less favorable [110] direction. TD samples predominantly deformed by slip. At CT, yield strength differed significantly between SD and TD samples, indicating mechanical anisotropy arising from grain morphology, local stress heterogeneities, and martensitic transformations (γ → ε → α′ and γ → α′). Simulations incorporating twinning- and transformation-induced plasticity (TWIP and TRIP) showed that [110]- and [111]-oriented grains relative to the loading direction exhibited higher resistance to deformation, consistent with lower twinning and martensite formation. At RT, twinning and screw dislocation glide were dominant, while at CT, anisotropy was governed by the interaction between hard and soft phases, with martensite variant selection playing a central role. The activation of TWIP and TRIP was strongly dependent on crystallographic orientation, with [001]-oriented grains showing greater deformation tendency.