On the Strength of a 316L-Type Austenitic Stainless Steel Produced by Selective Laser Melting

The developed microstructure and the tensile behavior of a 316L-type steel produced by selective laser melting were studied. This paper particularly aims to clarify the dislocation substructures in the developed steel, focusing on the density of dislocations, their arrangement in cells/subgrains, related internal distortions, and specific strengthening. The experimental samples were obtained using a 3D selective laser melting system ProX200 (laser power of 240 W, beam speed of 1070 mm/s, distance between tracks of 80 µm, and layer thickness of 30 µm) in a nitrogen atmosphere. The steel microstructure was characterized by a grain size of 20 μm and a high dislocation density of 5 × 1014 m−2 in the grain/subgrain interiors. The rather strong fiber texture of <012> along the building direction resulted in different Taylor factors of 2.89 and 3.30 for tension along the building direction and the side direction, respectively. The yield strength of 645 ± 5 MPa, the ultimate tensile strength of 750 ± 10 MPa, and an elongation of 40 ± 5% were obtained with a tensile test along the side direction. The rough calculation of the strengthening mechanisms suggested that the solid solution strengthening of 273 MPa and the dislocation strengthening of 262 MPa were the main contributors to the yield strength. Such a combination of strengthening from solid solution and homogeneously distributed numerous dislocations provides the processed steel with sufficient strengthening ability, leading to an outstanding strength–ductility combination.