Comparison of the neutron and ion irradiation response of nano-oxides in oxide dispersion strengthened materials
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ric Bordas, Patrick Trocellier, and Yves Serruys CEA, DEN, Service de Recherches de Métallurgie Physique, Laboratoire JANNUS, F-91191 Gif sur Yvette, France
Yann de Carlan CEA, DEN, Service de Recherches Métallurgiques Appliquées, F-91191 Gif sur Yvette, France
Alexandre Legris UMET, CNRS/UMR 8207, Univ. Lille 1, 59655 Villeneuve d’Ascq, France (Received 12 September 2014; accepted 6 June 2015)
The Oxide Dispersion Strengthened (ODS) materials are potential candidates as cladding tubes for Sodium-cooled Fast Reactors. The nano-oxides are finely dispersed within the grains and confer excellent mechanical properties to these alloys. Hence, assessing nano-particle stability under irradiation remains crucial to guarantee safe use of these materials. Although neutron irradiation remains a binding and challenging experimental study to conduct, difficulties can be overcome by ion beam processing. Ion beam processing of the ODS material allows to identify the radiationinduced Ostwald ripening as the mechanism governing the nano-particle response under irradiation. The result is the increase in size and a decrease in density of the finely dispersed Y2Ti2O7 nano-particles. Under neutron irradiation, radiation-induced Ostwald ripening appears to be less effective since a slight growth of nano-particles is observed. Further, our approach shows that nanoparticle growth kinetics should scale as u1/3, u being the radiation flux. This suggests that the low irradiation flux is at the origin of the slower growth kinetics of the neutron irradiated particles. Both neutron and ion irradiation induce a modification of the nanoparticles/matrix interfaces which are generally flat and sharp prior to irradiation and present steps after irradiation. This could alter the nano-particle coarsening during irradiation.
Contributing Editor: Djamel Kaoumi a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2015.183
Under neutron irradiation, Yamashita et al.2 reported, in the MA957 alloy, a decrease of the nano-oxide density after irradiation at 500 °C up to 104 dpa, even though they reported no clear change in the nano-oxide size. On the contrary, Gelles3 observed no significant change on the nano-oxide distribution at 480 °C for the high level dose of 200 dpa in the same alloy. Other authors4,5 observed no nanoparticle dissolution after irradiation, in agreement with Gelles’ results. Ribis and Lozano-Perez6 found that nano-oxides were still dispersed in the ferritic matrix of the MA957 alloy with a slight change on their size and their density after irradiation at 430 °C up to 75 dpa. Concerning, the chemical composition of nanoparticles after irradiation, atom probe tomography (APT) exams on neutron irradiated samples at 330 °C up to 32 dpa7 showed a high density of fine nanoclusters enriched in yttrium, oxygen, manganese, and chromium, indicating that this composition differs from that of the nonirradiated state since the vanadium had left the clusters. In parallel to the neutron irradiation experimental studies,
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