Microstructure and Anisotropy of the Mechanical Properties of 316L Stainless Steel Fabricated by Selective Laser Melting

Abstract

Significant anisotropy in mechanical properties was observed in 316L stainless steel (SS) that was subjected to selective laser melting (SLM) to produce a hierarchical structure, composed of molten pool, columnar grains, and a cellular substructure. Such anisotropy was induced by the geometric relationship between the boundary of the molten pool and the tensile force. The in situ tensile test showed initial deformation rapidly occurred at the boundary of the molten pool, followed by strain localization, and a lower ductility was obtained when loaded in the longitudinal direction (perpendicular to the molten pool). By contrast, the deformation was significantly constrained because of the geometry of the boundary of the molten pool, and substantial deformation occurred in the cellular substructure during loading in transverse direction (parallel to the molten pool). Finally, the quantitative analysis revealed that the high-level strength was attributed to the high-density dislocations and the fine cellular substructure.

Investigation of Material Properties of Wall Structures from Stainless Steel 316L Manufactured by Laser Powder Bed Fusion

“…Exemplary SEM images of the fracture surfaces of additive-manufactured T specimens are shown in Figure 14. In contrast to [50], where different fracture surfaces are observed for different orientations, all additive-manufactured T specimens in this work show very similar ductile fracture surfaces with very fine ductile dimples and some larger cavities caused by porosity, indicating the same ductile fracture mechanism. Therefore, the entire fracture surfaces reveal the characteristic features for a ductile shear fracture and no significant differences in fracture microstructure could be observed between the different orientations.…”

“…The mechanical properties, especially the elongation at fracture, are found to be anisotropic, resulting in around 5% higher YS and UTS and up to 20% higher elongation at fracture in the vertical direction parallel to the building direction in comparison to the vertical direction. This can also be explained by the columnar and therefore anisotropic microstructure, which is a result of the layer-by-layer manufacturing process of PBF-LB/M and is well described in the literature [30,31,34,50,52].…”

Selective Laser Melting of 316L Austenitic Stainless Steel: Detailed Process Understanding Using Multiphysics Simulation and Experimentation

“…One of them is gas bubbles, which are entrapped in the melt. Another common defect is due to reusing powder from the previous fabrications [38,[43][44][45][46][47][48][49][50][51].…”

The Effect of a Slow Strain Rate on the Stress Corrosion Resistance of Austenitic Stainless Steel Produced by the Wire Laser Additive Manufacturing Process

“…Additive manufacturing (AM) technologies developed in the last two decades have been aimed mainly at producing complex geometrics with minimal machining finishes using powder bed fusion (PBF) technologies, mostly selective laser melting (SLM) and electron beam melting (EBM) [1][2][3][4][5][6][7][8][9][10][11][12]. However, these relatively expensive PBF technologies do not adequately address the need to produce large components with less complicated geometrics at affordable production costs [13,14].…”