Structural and chemical evolution in neutron irradiated and helium-injected ferritic ODS PM2000 alloy

Abstract

An investigation of the influence of helium on damage evolution under neutron irradiation of an 11 at% Al, 19 at% Cr ODS ferritic PM2000 alloy was carried out in the High Flux Isotope Reactor (HFIR) using a novel in situ helium injection (ISHI) technique. Helium was injected into adjacent TEM discs from thermal neutron 58 Ni(n th ,γ 59 Ni(n th ,α) reactions in a thin NiAl layer. The PM2000 undergoes concurrent displacement damage from the high-energy neutrons. The ISHI technique allows direct comparisons of regions with and without high concentrations of helium since only the side coated with the NiAl experiences helium injection. The corresponding microstructural and microchemical evolutions were characterized using both conventional and scanning transmission electron microscopy techniques. The evolutions observed include formation of dislocation loops and associated helium bubbles, precipitation of a variety of phases, amorphization of the Al 2 YO 3 oxides (which also variously contained internal voids), and several manifestations of solute segregation. Notably, high concentrations of helium had a significant effect on many of these diverse phenomena. These results on PM2000 are compared and contrasted to the evolution of so-called nanostructured ferritic alloys (NFA).

Irradiation damage concurrent challenges with RAFM and ODS steels for fusion reactor first-wall/blanket: a review

“…Because oxide particles act as point-defect sinks, any changes to the nano-dispersoid microstructure will affect the overall radiation tolerance of the alloy in the entire operating temperature range for FW/B structures. The oxide particle stability, recently reviewed in [216], has been extensively researched using neutrons [194,196,199,204,205,[217][218][219][220][221][222][223][224][225][226][227][228][229][230], ions [219, and electron irradiations [261,262] in a variety of ODS steels. Extensive ion irradiation literature exists on a wide range of ODS steels where nano-dispersoids are reported to be stable over the irradiation temperature and dose ranges of RT-835 • C and ion doses from ∼2 to 200 dpa [205, 233, 234, 237, 240, 243, 247-249, 251, 259, 263].…”

“…However, substantial literature also exists over a similar ion irradiation temperature and dose range, where deterioration of the oxide particles is reported [205,219,222,226,231,235,238,239,241,242,245,250,257,261,262,264,265]. The majority of these reports typically show changes in the size or number density of the nano-dispersoids, while irradiations in the temperature range of RT-400 • C have also shown radiation-induced amorphisation (RIA) of the oxide particles in many ODS steels [196,229,235,243,251,261,264]. This includes RIA near RT of oxide particles in MA957 [243], ODS-Eurofer97 [251], 18%Cr-ODS [264] and electronic stopping power-induced amorphisation of oxides in DY ODS steels [235], while RIA using heavy ions at higher temperatures (⩾400 • C) of nano-dispersoids is reported in EM10-ODS [205] and DY ODS steels [196,205].…”

Post-irradiation microstructural examination of EUROFER-ODS steel irradiated at 300°C and 400°C

“…Highly dispersed oxide particles serve as trapping sites for vacancies and self-interstitial atoms, preventing the formation and coarsening of radiation-induced defects that lead to degradation of mechanical properties. Most studies of irradiated ODS materials are focused on demonstrating the stability of ODS particles [7,14,15] and to a lesser extent, on the formation of radiation-induced defect [8,16]. Our work intends to fill the current knowledge gap and contribute to a better understanding of the radiation resistance mechanism of ODS alloys.…”