The natural aging of austenitic stainless steels irradiated with fast neutrons

Much of today's research in nuclear materials relies heavily on archived, historical specimens, as neutron irradiation facilities become ever more scarce. These materials are subject to many processes of stress- and irradiation-induced microstructural evolution, including those during and after...

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Bibliographic Details
Published in:Journal of nuclear materials 2018-02, Vol.499, p.284-293
Main Authors: Rofman, O.V., Maksimkin, O.P., Tsay, K.V., Koyanbayev, Ye.T., Short, M.P.
Format: Article
Language:English
Subjects:
Aging
Aging (metallurgy)
Aging (natural)
Austenitic stainless steel
Austenitic stainless steels
Breeder reactors
Fast breeder
Fast neutrons
Irradiation
Low temperature
Migration
Neutron irradiation
Neutrons
Nuclear engineering
Stress
Stress state
Stresses
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Summary:Much of today's research in nuclear materials relies heavily on archived, historical specimens, as neutron irradiation facilities become ever more scarce. These materials are subject to many processes of stress- and irradiation-induced microstructural evolution, including those during and after irradiation. The latter of these, referring to specimens “naturally aged” in ambient laboratory conditions, receives far less attention. The long and slow set of rare defect migration and interaction events during natural aging can significantly change material properties over decadal timescales. This paper presents the results of natural aging carried out over 15 years on austenitic stainless steels from a BN-350 fast breeder reactor, each with its own irradiation, stress state, and natural aging history. Natural aging is shown to significantly reduce hardness in these steels by 10–25% and partially alleviate stress-induced hardening over this timescale, showing that materials evolve back towards equilibrium even at such a low temperature. The results in this study have significant implications to any nuclear materials research program which uses historical specimens from previous irradiations, challenging the commonly held assumption that materials “on the shelf” do not evolve. [Display omitted] •Stress and low temperature cause long timescale evolution of irradiated materials.•Data challenge the assumption that irradiated materials don't evolve “on the shelf.”•Stress has a significant influence on austenitic steels during storage.•An important aspect of material aging is the local redistribution of elements.
ISSN:0022-3115
1873-4820
DOI:10.1016/j.jnucmat.2017.11.006