Photon Factory Activity Report 2022 #40 (2023)

BL-27B/2022G071

Effect of Energetic Ion irradiation on Lattice Structure and Hardnessof Double-Phased Zr-Ni Alloy
F. Hori1, H. Obayashi1, T. Matsui1, Y. Kaneno1, T. Wada2, H. Kato2, N. Ishikawa3, A. Iwase1,4,*
1Osaka Metropolitan University, Sakai, Osaka, 599-8570, Japan
2
Tohoku University, Sendai, Miyagi, 980-8577, Japan
3
Japan Atomic Energy Agency, Tokai-mura, Ibaraki 319-1195, Japan
4The Wakasa Wan Energy Research Center, Tsuruga, Fukui, 914-0192, Japan
1 Introduction
Our previous papers have reported that non-thermal
equilibrium lattice structures are induced by energetic ion
irradiation in some Ni-based intermetallic compounds. The
irradiation-induced lattice structures strongly depend on
the target materials. The intrinsic lattice structures of Ni3Vand Ni3Al are the tetragonal (D022) and the ordered FCC(L12) structures, respectively. By the energetic ion
irradiation, they change to the disordered FCC (A1)structure 1,2). In the case of Ni3Nb, and Ni3Ta, the intrinsic
structures (orthorhombic and monoclinic structures,
respectively) are amorphized by the irradiation3,4). All theNi-based intermetallic alloys we have investigated so far
show the single-phased structures before the irradiation. In
the present study, we chose the double-phased Zr-Ni alloy,
and the effect of 100 MeV Ni ion irradiation on its lattice
structure and hardness was investigated.
2 Experiment
A Ni30Zr70 alloy was prepared by using pure Ni and Zr
metals. An alloy ingot was made by arc melting in an argon
gas atmosphere. The ingot was thermally aged at 1100 K
for 12 hours in vacuum of <3x10- 4 Pa. After the thermal
aging, the ingot was cut into some sheets with thedimension of 5x5x0.5 mm3. The surfaces of alloy sheets
were polished by using #2000 emery-paper and #3000
alumina buff. The surface morphology of the alloy sheets
was observed using an optical microscope.
The alloy sheets were irradiated at room temperature
with 100 MeV Ni ions by using 20 MV tandem accelerator
at Nuclear Science Research Institute of Japan Atomic
Energy Agency. The ion fluences were 1 × 1013, 1 × 1014 ,2 × 1014 and 5 × 1014 cm-2.
The lattice structures of the unirradiated and irradiatedsamples were examined by using an X-ray diffraction
method (XRD). The CuK x-ray was used for thediffraction. To investigate the local structure around Ni
atoms, the extended x-ray absorption fine structure(EXAFS) measurements were performed near the Ni K
absorption edge at the 27B beamline of the synchrotron
radiation facility of High Energy Accelerator Research
Organization (KEK-PF). The EXAFS spectra wereobtained by using the fluorescence method with a 7element germanium x-ray detector.
The irradiation-induced hardness change was examinedusing a Vickers hardness tester with a load of 10 gf and thetime interval of indentation was kept at 10 seconds.

3 Results and Discussion
Fig. 1 shows the surface image of the unirradiated Ni-Zr
sample obtained by an optical microscope. The figure
clearly shows that the Ni-Zr sample consists of two phases.
The existence of the two phases in the unirradiated sample
was confirmed by the XRD measurement. As can be seenin Fig.2, the XRD peaks for the tetragonal phase (NiZr2)
and those for the hexagonal phase (Zr) are observed in theXRD spectra.
.

NiZr2
Zr
Fig. 1: Surface image of Ni-Zr alloy

Fig.2: XRD spectra for unirradiated Ni-Zr alloy

Photon Factory Activity Report 2022 #40 (2023)

Fig. 3 shows the effect of 100 MeV Ni ion irradiation on
the XRD spectrum. Even after the ion irradiation, XRD
peaks corresponding to the tetragonal and hexagonal lattice
structures are clearly observed, which means that thelattice structures keep unchanged by the irradiation. Thisirradiation effect is quite different from the case of theother Ni-based intermetallic compounds.

Fig.3: XRD spectra for unirradiated and irradiatedNi-Zr alloy. Fluences of 100 MeV Ni ions are shownin the figure.

Fig.4: Magnified XRD spectra of unirradiated andirradiated Ni-Zr alloy around 44.2 degree.

Fig. 4 shows the magnified XRD spectra around 44.2
degree. With increasing the ion fluence, the XRD peakshifts to lower angles. This experimental result indicatesthat the lattice is expanded by the ion irradiation.
The effect of 100 MeV Ni ion irradiation on the lattice
structure is also observed in the EXAFS spectrum. Fig. 5
shows that the intensity of EXAFS-FT spectrum decreases
by the irradiation. This result means that the atomic
arrangements near Ni atoms are disordered by theirradiation.

Fig. 5: EXAFS-FT spectra for unirradiated andirradiated Ni-Zr alloy.
Fig. 6 shows the micro Vickers hardness of Ni-Zr alloy
as a function of 100 MeV Ni ion fluence. Although thetetragonal and hexagonal structures remain unchanged by
the irradiation, the hardness increases with increasing theion fluence. The investigation for the mechanism of the ion
irradiation-induced hardness change is now in progress.

Fig. 6: hardness of Ni-Zr alloy as a function of 100 MeV
Ni ion fluence.

Photon Factory Activity Report 2022 #40 (2023)

Acknowledgements
The authors thank the technical staff of the tandem
accelerator at Nuclear Science Research Institute of Japan
Atomic Energy Agency. They also thank Drs. Y. Okamoto
and N. Usami for their help.
References[1] A. Hashimoto et al., Nucl. Instrum. Methods B338, 72(2014).
[2] H. Yoshizaki et al., Nucl. Instrum. Methods B354, 287(2014).
[3] H. Kojima et al., Nucl. Instrum. Methods B372, 72(2016).
[4] H. Kojima et al., Mater. Trans. 58, 739 (2017).

* iwase@omu.ac.jp