Hydrogen's influence on reduced activation ferritic/martensitic steels' elastic properties: density functional theory combined with experiment

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Hydrogen's influence on reduced activation ferritic/martensitic steels' elastic properties: density functional theory combined with experiment. Reduced activation ferritic/martensitic (RAFM) steels are widely applied as structural materials in the nuclear industry. To investigate hydrogen's effect on RAFM steels' elastic properties and the mechanism of that effect, a procedure of first principles simulation combined with experiment was designed. Density functional theory models were established to simulate RAFM steels' elastic status before and after hydrogen's insertion.
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Nuclear Engineering and Technology
journal homepage: www.elsevier.com/locate/net
Original Article
Hydrogen's inuence on reduced activation ferritic/martensitic
steels' elastic properties: density functional theory combined
with experiment
Sinan Zhu, Chi Zhang*, Zhigang Yang, Chenchong Wang
Key Laboratory of Advanced Materials of Ministry of Education, School of Materials Science and Engineering, Tsinghua University, No. 1 Qinghua Yuan,
North Zhongguancun Street, Beijing 100084, China
a r t i c l e
i n f o
a b s t r a c t
Article history:
Reduced activation ferritic/martensitic (RAFM) steels are widely applied as structural materials in the
Received 1 June 2017
Received in revised form
31 July 2017
Accepted 22 August 2017
Available online 16 October 2017
nuclear industry. To investigate hydrogen's effect on RAFM steels' elastic properties and the mechanism
of that effect, a procedure of rst principles simulation combined with experiment was designed. Density
functional theory models were established to simulate RAFM steels' elastic status before and after hy-
drogen's insertion. Also, experiment was designed to measure the Young's modulus of RAFM steel
samples with and without hydrogen charging. Both simulation and experiment showed that the solu-
Keywords:
Density Functional Theory
Experiment
Elastic Properties
bility of hydrogen in RAFM steels would decrease the Young's modulus. The effect of hydrogen on RAFM
steels' Young's modulus was more signicant in water-quenched steels than it was in tempering steels.
This indicated that defects inside martensite, considered to be hydrogen traps, could decrease the
cohesive energy of the matrix and lead to a decrease of the Young's modulus after hydrogen insertion.
Hydrogen
© 2017 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the
RAFM Steels
1. Introduction
of hydrogen on steel elastic properties signicantly varied for
different steels. With respect to hydrogen embrittlement, very few
Reduced activation ferritic/martensitic (RAFM) steels are widely
investigations have focused on contemporary structural materials
applied as structural materials in fusion reactors, owing to their
of the nuclear industry. Therefore, the effect of hydrogen on RAFM
excellent performance in withstanding heat ux and neutron beam
steels and the mechanism of that effect are still unclear, which will
[1e3]. Considering the service environment, hydrogen tends to
probably be a limitation in fusion reactor development. Meanwhile,
exert some inuence on RAFM steels' properties, especially the
simulation and experiment on hydrogen embrittlement have usu-
mechanical properties. Indeed, hydrogen's effect on steels has been
ally been operated in isolation and have lacked a necessary com-
investigated widely for a long time [4,5].
bined approach.
However, the mechanism of hydrogen's inuence on steel
In this work, we focused on hydrogen's inuence on RAFM steels'
properties has remained unclear so far. Various conclusions have
elastic properties, adopting both density functional theory (DFT)
been presented with respect to different steel compositions, heat
simulation and experiment. The effect of hydrogen on RAFM steels'
treatment processes, experiment methods, and simulation pro-
elastic modulus was studied, and the mechanism of that effect was
cedures [6e9]. Usui and Shigeru's experimental work [6] based on
analyzed by comparison of simulation and experimental results.
FeeCreMn austenite indicated that hydrogen charging increased
the Young's modulus. However, Ortiz and Ovejero-Garcia's exper-
imental results [7] on AISI 1005 and 1070 steels drew an opposite
2. Material and methods
conclusion: hydrogen decreased the Young's modulus. D. Psiachos
et al.'s ab initio study [8] manifested that interstitial hydrogen
decreased the elastic constants of a-iron. As mentioned, the effect
The main composition of our RAFM is shown inTable 1. Based on
the material, DFT computational models and corresponding ex-
periments were designed.
Two models were built as shown in Fig. 1. Model A was a
* Corresponding author.
2  2  2 supercell, of which the unit cell was a body-centered
E-mail address: chizhang@tsinghua.edu.cn (C. Zhang).
cubic (BCC) Fe cell. The Fe atom at the center position was replaced
1738-5733/© 2017 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/