3D Dark-field X-ray Microscopy Intra-granular Dislocation Mapping in L-PBF AISI 316L Coupled with Texture Analysis and Computed Tomography

Dislocations in Laser Powder Bed Fusion (L-PBF) AISI 316L closely relates to the material’s stress state, response and damage at the inter- and intra-granular scales. Assessing the dislocation state and activity at these scales helps understand the material behaviour at larger length-scales. Nevertheless, most experimental studies have utilised surface or destructive methods, unable to probe the bulk non-invasively. We conduct the first Dark-Field X-ray Microscopy (DFXM) investigation to non-destructively assess the intra-granular dislocation density within an L-PBF AISI 316L grain in the bulk. The research unveiled sub-granular cells with orientation spread up to 4°, and intra-granular dislocation arrangements, signalling Type III Residual Stress (RS) in the bulk. Additional texture analysis indicated a predominant {110} orientation within the grain. Computed tomography on a miniaturised sample (200x200 mm2 cross-section) enabled the statistical characterisation of its porosity. Pores were found close to the sample surface and geometrically regular, with sphericity mostly greater than 0.5.