03pC02
核融合材料の微小押し込み変形挙動
Nanoindentation on fusion reactor materials
落合 良介1，笠田 竜太1，小西1

1

哲之1，安堂1

正巳2，濱口 大2，谷川2

2

R. Ochiai , R. Kasada , S. Konishi , M. Ando , D. Hamaguchi , H. Tanigawa
1

博康2

2

京大エネ理工研，2原子力機構
1

IAE, Kyoto Univ., 2JAEA

1. Introduction
The ion-irradiation techniques using MeV self-ion(ex. Fe ion for steels) beam are of great use inexperimentally simulating neutron irradiation effects
on fusion reactor materials because of theiradvantages:
thehighdamagerate,
noinduced-radioactivity, precisely-controllable irradiation
conditions, and co-implantation with helium and/orhydrogen. In order To investigate the mechanicalproperties of ion-irradiated materials, nanoindentation
has been used to measure the hardness of materials inthe surface up to a few micron meters. However it has
been believed that the nanoindentation hardness of
ion-irradiated materials has difficulty to compare withthe bulk mechanical properties including Vickers
hardness of the neutron-irradiated materials because of
the indentation size effect (ISE).
One of the authors (RK) suggested a useful model toevaluate bulk-equivalent hardness for the ion-irradiatedmaterials, which is mechanistically related to Vickers
hardness [1]. The present study examines a modified
model to evaluate depth-dependent bulk-equivalenthardness of the ion-irradiated F82H reduced-activation
ferritic steels with a consideration of damage gradienteffect (DGE).
2. Experimental Procedure
The materials used in the present study were F82H
(nominal compositions: Fe-8Cr-2W-0.2V-0.05Ta-0.1C)
and 1 wt.% Ni added F82H (F82H–1Ni). It is known
that Ni addition has a great impact on irradiation
hardening behavior. Ion-irradiation experiments wereperformed with a single-ion beam of 10.5 MeV Fe3+ in
the TIARA facility at JAEA. The irradiation
temperature was controlled at 270 °C. The nominal
dose rate and nominal dose were 1.3 × 10−3 dpa/s and 5dpa, respectively. The nominal values stand for theones at approximately 1 m below the irradiatedsurface.
The nanoindentation hardness was measured byusing a NanoIndenter G200 (Agilent Technologies)
with a Berkovich-type indentation tip. The continuousstiffness measurement (CSM) was used tocontinuously obtain the hardness (H) - depth (h)profile.

3. Results and Discussion
Fig. 1 shows indentation-depth profile of theaveraged nanoindentation hardness of F82H-1Ni steel
before and after the ion-irradiation in TIARA. The
unirradiated F82H-1Ni showed increase in hardness
with decreasing indent size or depth, i.e., ISE. Our new
method can evaluate a bulk-equivalent hardness ateach indentation depth, H0(h) from the gradient ofNix-Gao plot at each (1/h) as
H 0 ( h )  H ( h) 2 

1 dH (h) 2
h d (1 / h)(1).

The calculated H0(h) are plotted against h in Fig. 2.
The increase of H0(h) in the shallow depth region up toapproximately 0.2 m in the ion-irradiated materials
suggests an existence of DGE.

Fig. 1 (left) Depth dependence of nanoindentation
hardness of F82H-1Ni before and after ion-irradiation.
Fig. 2 (right) The bulk-equivalent hardness ofF82H-1Ni shown in Fig. 1.
4. Conclusion
Thus, we have successfully developed a new model
to evaluate the depth-dependent bulk-equivalenthardness of ion-irradiated materials. Further advanceon utilizing nanoindentation method will be shown inthe conference.
Reference[1] R. Kasada, Y. Takayama, K. Yabuuchi, A. Kimura,
Fusion Eng. and Des., 86 (2011) 2658–2661.