Anisotropic Radiation-Induced Changes in Type 316L Stainless Steel Rods Built by Laser Additive Manufacturing

In this experiment, Type 316L stainless steel rods were fabricated through laser additive manufacturing (LAM) in three different orientations, and microstructural and mechanical changes induced by high dose ion irradiation were characterized based on orientation. The rods were irradiated with Fe²⁺ self-ions to a peak dose of 80 displacements per atom at 475°C. Results were compared to concurrently irradiated conventionally manufactured control specimens. Electron backscatter diffraction of the rods yielded statistically relevant information related to grain microstructure and texture. Transmission electron microscopy revealed a high density of elongated radiation-produced defects in the LAM specimens that were aligned with the major axes of the defects parallel to the build direction. Mechanical testing of LAM rods revealed anisotropic radiation-induced hardening, where hardening is greatest perpendicular to the build direction and least parallel to the build direction. Several radiation-induced hardening phenomena are considered that contribute to the observed anisotropic strengthening.