Micro Laser Powder Bed Fusion of Stainless Steel 316L: Cellular Structure, Grain Characteristics, and Mechanical Properties

Micro laser powder bed fusion (mu-LPBF) enables the fabrication of the components with higher resolution and accuracy compared with conventional laser powder bed fusion (c-LPBF). This study demonstrated the feasibility of fabricating materials with excellent mechanical properties due to the fine microstructures generated by mu-LPBF. The near fully dense austenite stainless steel 316L with high strength was successfully achieved. The tensile tests showed that the specimens had the yield strength ranging from 645 MPa to 690 MPa, ultimate tensile strength between 765 MPa and 795 MPa, and total elongation over 40%. The high strength without the sacrifice of the elongation was attributed to the fine cellular structures. Both cell size and cell wall thickness were critical factors for the yield strength. The thin wall contributed to the minor increase in the yield strength when compared with c-LPBF fabricated specimens in the literatures. The hatch spacing minorly affected the cellular structure but did affect the grain size and texture. Due to the similar characteristics of the cellular structure, the yield strength was not strongly affected by the hatch spacing. The critical stress for deformation twinning was determined by the texture varying as the hatch spacing, which was the reason for the lower elongation of the samples under the largest hatch spacing.