Fabricating irradiation-tolerant ODS Fe-Cr steel with engineered Y-Ti-O nanoprecipitates by laser powder bed fusion

• Highly dense ODS Fe-Cr steel components were prepared by LPBF. • Uniformly dispersed Y-Ti-O nanoprecipitates with high density were in situ constructed. • Superior radiation tolerance and mechanical properties were achieved via tailored microstructures. • High-quality interfaces between Y-Ti-O nanoprecipitates and Fe-Cr matrix improved radiation tolerance and creep resistance. Developing advanced structural materials for next-generation nuclear reactors that simultaneously achieve superior radiation tolerance, excellent mechanical properties, and manufacturable components remains a significant challenge. Additive manufacturing via laser powder bed fusion (LPBF) offers a promising pathway to engineer high-performance reactor materials with tailored microstructures. Herein, oxide dispersion-strengthened (ODS) Fe-Cr steels with near-full density (>99 %) and uniformly dispersed Y-Ti-O nanoprecipitates (number density approximately 4 × 10 20 /m 3 ) were fabricated by LPBF using gas-atomized reaction-synthesized powders. In-situ formed Y-Ti-O nanoprecipitates during the intrinsic heat treatment of the LPBF process enhanced the energy barrier to plastic deformation in ODS Fe-Cr steel by impeding dislocation motion and climb, thereby conferring superior high-temperature strength and creep resistance compared to the Fe-Cr steel counterpart. Furthermore, energetic Au + and He + ion irradiations, coupled with transmission electron microscopy and nanoindentation analyses, demonstrate that the LPBF-engineered high-density interfaces between Y-Ti-O nanoparticles and the Fe-Cr matrix serve as efficient sinks for irradiation-induced defects. This interface-mediated defect annihilation mechanism mitigated radiation damage, ensured microstructural stability, and reduced irradiation hardening. This work provides valuable insights into the design and manufacturing of irradiation-resistant ODS steel components via LPBF for advanced nuclear reactors.