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Study on Cu Precipitation in Energetic Electron
Irradiated FeCu Alloy by Means of
X-ray Absorption Spectroscopy
A. Iwase a) , S. Kosugi a) , S. Nakagawa a) , N. Ishikawa b) and Y. Okamoto c)
a) Department of Materials Science, Osaka Prefecture University,
b) Advanced Science Research Center, JAEA,
c) Synchrotron Radiation Research Center, QuBS, JAEA
1, 2)
In the previous reports , we showed the change in
Vickers hardness for electron-irradiated FeCu alloys and
discussed the dependence of the hardness on
electron-fluence and Cu concentration. In the present
experiment, FeCu alloy specimens were irradiated with
electrons up to much higher fluences and the status of Cu
precipitation was studied by means of extended X-ray
absorption fine structure (EXAFS) measurements.
Specimens were prepared from Fe-0.6wt.%Cu alloy.
They were annealed at 850 ºC and were quenched into 0 ºC
water. The specimens were irradiated with 2 MeV
electrons to the fluence of 4.5 × 10 19 /cm 2 using two electron
accelerators at JAEA-Takasaki. After the irradiation, the
micro Vickers hardness was measured as a function of
electron fluence. EXAFS spectra at Cu K absorption edge
were collected using the 27B beamline at the Photon
Factory of High Energy Accelerator Research Organization
(KEK-PF). The spectra were obtained using 7 element
germanium detector in the fluorescence mode. For
comparison, EXAFS spectra for pure Cu and Fe foils were
also measured in the transmission mode.
Figure 1 shows the dependence of change in Vickers
microhardness on electron fluence for Fe-0.6wt.%Cu
specimens. The hardness increases monotonically with
increasing the electron fluence, and tends to be strongly
saturated at high fluence. Figure 2 shows the k 3 -weighted
Foulier transforms corresponding to the EXAFS spectra for
Change in Vickers Hardness
100
80
60
40
20
0
0 1 2 3 4 5
Electron Fluence (10 19 /cm 2 )
Fig. 1 Change in Vickers hardness for Fe-0.6wt.%Cu
irradiated with 2 MeV electrons at 250 ºC.
JAEA-Review 2010-065
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pure Fe, pure Cu and Fe-0.6wt.%Cu specimens which were
irradiated with electrons. For small electron fluence
(2.7 × 10 17 /cm 2 ), the shape of EXAFS spectrum for FeCu
alloy is similar to that for pure Fe. With increasing the
electron fluence, however, the EXAFS shapes become
similar to that for pure Cu. The present result suggests that
Cu precipitates with BCC structure appear by the electron
irradiation with the small fluence. With increasing the
electron fluence, the structure of Cu precipitates gradually
change from BCC to FCC.
Fig. 2 Foulier transform of Cu K-edge EXAFS spectra for
electron irradiated Fe-0.6wt.%Cu. For comparison,
EXAFS spectra for pure Fe and pure Cu are also shown.
References
1) S. Nakagawa et al., Proc. Mater. Res. Soc. Symp.
1043-T09-04 (2008).
2) S. Nakagawa et al., JAEA Takasaki Ann. Rep. 2008
(2009) 136.