Atom probe tomography of radiation-sensitive KS-01 weld

Abstract

An atom probe tomography characterization has been performed on a neutron-irradiated (fluence = 0.8 × 10¹⁹ n cm⁻² (E > 1 MeV)) high copper (0.37%), high manganese (1.64%), high nickel (1.23%) and high chromium (0.47%) KS-01 test weld. This weld exhibited a high sensitivity to neutron irradiation. Atom probe tomography revealed that there was an unusually high supersaturation of copper in the matrix after the stress relief treatment, which resulted in a high number density (3 × 10²⁴ m⁻³) of Cu–Mn–Ni-enriched precipitates after neutron irradiation. Their average size and composition were estimated to be ⟨lg⟩ = 2.6 ± 0.5 nm and Fe-17.0 ± 9.7 at% Cu, 31.9 ± 13.8% Ni, 31.7 ± 11.8% Mn. Phosphorus clusters and a Cr-, Mn-, Ni-, Cu-, C-, N-, Si- and Mo-enriched atmosphere, possibly associated with a dislocation, were also observed in the neutron irradiated material. Nickel, manganese, silicon, phosphorus and carbon segregation to a grain boundary were observed in the unirradiated condition. The microstructural and mechanical response to irradiation was consistent with other lower solute level steels.

Acknowledgements

Research at the Oak Ridge National Laboratory SHaRE Collaborative Research Center was sponsored by the Division of Materials Sciences and Engineering, U.S. Department of Energy, under contract DE-AC05-00OR22725 with UT-Battelle, LLC and by the Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission under inter-agency agreement DOE 1886-N695-3W with the U.S. Department of Energy.