The Influence of Geometry and Orientation on the Cellular Substructure and Local Mechanical Properties of Additively Manufactured AISI 316L

The complex geometries feasible with Laser Powder Bed Fusion (PBF-LB/M) lead to varying sizes of scanned cross sections within the layers and hence differing cooling rates. Since PBF-LB/M results in intragranular cell structures, which cause relatively high strengths in the austenitic steel AISI 316L, the influence of changes in the specimen size on the cell structure was investigated. The results obtained from the geometries realized in this work showed no significant influence of the specimen size on the cell sizes. To analyze the relation between the cell structure and the mechanical properties, cyclic indentation tests (CIT) were performed accordingly, revealing no clear influence of the specimen size on the mechanical properties and no correlation between the cell size and the mechanical properties. Additionally, the impact of the cell size on the well-known anisotropy in mechanical properties of AISI 316L produced via PBF-LB/M was investigated. While the cell size was observed to be independent of the specimen orientation on the build plate, the orientation between the direction of loading and the building direction reveals a slight influence on the mechanical properties obtained from CIT. In comparison to the properties determined using CIT, a stronger influence of the orientation between the load and the building direction was observed in tensile tests, which was not caused by the intragranular cells. It was concluded that the anisotropy in the tensile properties is mainly affected by the texture, the elongated grains, and the layer orientation.