Microstructural studies on early-stage deformation in thin-walled LPBF-manufactured SS316L considering its printing orientation

This study investigates the influence of build orientation on the microstructure and early-stage deformation behaviour of austenitic stainless steel 316 L (SS316L) produced via laser powder bed fusion (LPBF). Three LPBF specimen orientations: horizontal (XY), inclined at 45° (ZX), and vertical (Z) were compared to conventionally produced wrought SS316L. Mechanical testing was conducted under uniaxial tension to fracture and to a controlled axial strain of 1 % to capture the onset of plasticity. Electron backscatter diffraction (EBSD) was performed before and after deformation to quantify grain boundary character, misorientation distribution, and grain morphology evolution. The LPBF material exhibited notable differences in yield strength and strain hardening, with the Z-oriented specimens exhibiting the lowest mechanical performance due to insufficient interlayer bonding and elongated melt pool boundaries aligned with the build direction. In contrast, the XY and ZX orientations showed relatively higher strength and more uniform deformation behaviour. EBSD revealed that early-stage plastic deformation led to the intragranular misorientation accumulation but the degree of it varied significantly with orientation. Wrought SS316L displayed the highest overall mechanical properties and more homogeneous deformation due to its equiaxed, recrystallized microstructure.