Deformation behavior and irradiation tolerance of 316 L stainless steel fabricated by direct energy deposition

Additive manufacturing (AM) techniques have been widely used to fabricate structural components with complex geometries. Understanding AM materials under extreme environments is crucial for their implementation in various engineering sectors. In this study, the deformation behavior and irradiation damage of 316 L stainless steel (SS) fabricated by the direct energy deposition (DED) process are investigated. The fabrication-induced nanopores with an average diameter of 200 nm exhibit a core-shell structure with a local tensile strain. The precession electron diffraction (PED) reveals that austenite-to-martensite phase transformation preferentially occurs around the nanopores under tension test at room temperature. Proton irradiation experiments performed at 360 °C to a fluence of 1.09 × 10¹⁹ cm⁻² and 5.42 × 10¹⁹ cm⁻² show that the DED fabricated 316 L SS exhibits a stronger void-swelling resistance and lower dislocation loop density than its wrought counterpart. AM-induced features, such as nanopores and sub-grain boundaries, could serve as defect sinks to absorb irradiation-induced defects. The design of microstructure using AM processes opens up new avenues for the development of irradiation tolerant materials for nuclear applications.