Morphological and Crystallographic Effects in the Laser Powder-Bed Fused Stainless Steel Microstructure

Abstract

One of the key aspects in additive manufacturing of stainless steels is the relationship between process parameters and the resulting microstructure. The selected process parameters typically cause a rapid solidification of the material, which leads to a microstructure that is highly textured both morphologically and crystallographically. While the morphological texture is characterised by a mainly columnar shape of the grains, the crystallographic texture is marked by a preferred grain orientation in the <001> direction (fibre texture). Due to the texture effects, pronounced anisotropic mechanical properties are present in the material. In this report, a series of virtual microstructures with different morphological and crystallographic features are generated to develop a fundamental understanding of the individual texture effects on the mechanical properties. The grain morphology is based on Voronoi tessellations, and the crystallographic texture is captured with crystal plasticity. Furthermore, the numerical predictions are compared with experimental studies. The mechanical properties predicted on the basis of the virtual microstructures show that the crystallographic effect is much more dominant than the morphology of the individual grains. Consistent with the experiments, the highest load-bearing capacity of the material occurs when the macroscopic loading acts under an angle of 45∘ to the preferred orientation of the crystals.