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| Microstructure and anisotropic mechanical properties of laser powder bed fusion 304L stainless steel |
| MA Yue, YUAN Tiechui, HUANG Yang, TAN Yun, ZOU Liang |
| State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China |
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Abstract In this paper, 304L stainless steel was fabricated by laser powder bed fusion (LPBF) technology using gas atomized powder as raw material. The effects of laser volumetric energy density on the microstructure of the alloy were investigated by X-ray diffratometer, backscattered electron diffratometer, scanning electron microscope, and transmission electron microscope, and the optimal process window was determined. Stainless steels with printing angles of 0°, 45°, and 90° were fabricated using this process parameter to study the influence of forming angle on the microstructure and mechanical properties of stainless steel. The results show that LPBF 304L stainless steel is mainly composed of austenite and a small amount of ferrite. When the laser volumetric energy density is 93.7 J/mm3, the stainless steel has the least pores and other defects, the lowest porosity, and the highest hardness. The tensile strength, yield strength, and elongation of stainless steel with a printing angle of 0° are (722.6±2.5) MPa, (580.3±1.5) MPa, and (58.6±2.3)%, respectively. The tensile strength, yield strength, and elongation of stainless steel with a printing angle of 45° are (714.3±2.5) MPa, (572.0±2.6) MPa, and (49.2±2.8)%, respectively. The tensile strength, yield strength, and elongation of stainless steel with a printing angle of 90° are (629.0±2.0) MPa, 527.7±3.1) MPa, and (67.4±3.5)%, respectively. Stainless steel with a printing angle of 0° shows finer grains, a higher proportion of low-angle grain boundaries, and a larger dislocation density, which helps to improve the material strength. Two kinds of subgrain structures, cellular subgrains and columnar subgrains, exist in LPBF 304L stainless steel. The differences in grain morphology, grain orientation, dislocation density, and subgrain structure are the reasons for the anisotropic mechanical properties of LPBF 304L stainless steel.
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Received: 27 March 2025
Published: 13 October 2025
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2025, Vol. 30 
