Austenitic steels are the most advanced candidates for Generation IV sodium fast reactor’s fuel cladding[1]. However, these steels undergo swelling under irradiation after an incubation period that will limit the fuel burnup[2]. An addition of titanium in austenitic steels increases their incubation period but the mechanism is not yet completely understood: titanium can act in solid solution and/or via the precipitation of titanium carbides[3]. A previous study revealed the strong impact of titanium in solid solution on the behavior under irradiation of nickel (Ni0.4%Ti [wt.%]): a model alloy of austenitic steels[4].

In this study, we focus on the effect of a combined addition of titanium and carbon on the microstructure evolution of nickel after irradiation. A Ni-0,4Ti-0,1C (wt.%) alloy was irradiated with Ni2+ ions in a Transmission Electron Microscope using the JANNuS-Orsay facility up to 0.06 dpa. The sample was finely analyzed in terms of precipitation and dislocation loops’ characteristics (nature, Burgers vectors and size). The characterizations reveal on the one hand the formation of perfect loops’ agglomeration that raises questions about their formation mechanism; and on the other hand a difference in dislocation loops’ nature between Ni-0.4Ti and Ni-0.4-0.1C alloys that can be explained by a precipitation of titanium carbides.

[1] CEA, 4th Generation sodium-cooled fast reactors / The Astrid technological demonstrator, (2021) 96.

[2] P. Dubuisson, Le gonflement des aciers austénitiques, Rev. Metall. 108 (2011) 33–37. https://doi.org/10.1051/metal/2010019.

[3] A. Hishinuma et K. Fukai, « Effect of Solute Titanium on Void Swelling in 316 Stainless Steel », Journal of Nuclear Science and Technology, vol. 20, no 8, p. 668‑673(1983, doi: 10.1080/18811248.1983.9733448.

[4] K. Ma et al, « Drastic influence of micro-alloying on Frank loop nature in Ni and Ni-based model alloys », Materials Research Letters, vol.8, no 5, p. 201‑207, mai 2020, doi:10.1080/21663831.2020.1741042.