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Manufacturing, microstructure characterization, and tensile testing of additively manufactured SS316L: Investigating strength, anisotropy, and fracture behaviour
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School of Engineering |
Master's thesis
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en
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82
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This thesis presents an in-depth experimental investigation into the process–mi-crostructure–property relationships of stainless steel 316L components fabricated using the Laser Powder Bed Fusion (LPBF) technique. The work is divided into two main phases. In the first phase, a series of cuboid samples were produced using varied LPBF process parameters to explore the effects of volumetric energy density (VED) on microstructural characteristics such as porosity, melt pool morphology, and sub-grain structure. A detailed examination was undertaken by employing Light Optical Microscopy (LOM) and Scanning Electron Microscopy (SEM) with the samples being cut along and perpendicular to the build direction.
The second phase focused on mechanical behaviour and anisotropy. In this regard, smooth dog-bone (SDB) tensile samples were made with seven different angles (0° to 90° relative to the build platform) and subjected to uniaxial tension test. The deformation of tensile specimens was measured by Digital Image Correlation (DIC) during the loading process, and some aspects of the fracture processes were also examined with a Scanning Electron Microscope (SEM). The results revealed a strong dependence of tensile strength and ductility on build orientation, highlighting directional mechanical anisotropy. Fractography confirmed that failure modes transitioned from lower ductility in the 0° samples to more ductile in the 45° and 90° orientations, consistent with melt pool and grain structure observations.
Overall, the outcomes reinforce the point of significance in calibration of process factors to obtain the desired microstructure and mechanical properties in printed SS316L. This study provides valuable guidelines for tailoring LPBF process inputs to control anisotropy and improve reliability in structural applications.