JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

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Nano-crystalline Formation of Metallic Glasses
by Ion Implantation
S. Nagata a) , Y. Murayama a) , B. Tsuchiya a) , T. Shikama a) , M. Sasase b) ,
A. Inouye c) and S. Yamamoto c)
a) Institute for Materials Research, Tohoku University, b) The Wakasa-wan Energy Research
Center, c) Environment and Industrial Materials Research Division, QuBS, JAEA
Metallic glasses have created considerable interest
because of their excellent physical and chemical properties
such as mechanical strength and corrosion resistance owing
1)
to their unique amorphous nature . Generally, the
amorphous phase of an alloy can be obtained from the liquid
state by rapidly cooling. Solid state amorphization
techniques such as, mechanical alloying and hydrogenation
have been extensively studied as novel processing methods.
Ion implantation is an alternative method to form
non-equilibrium phases by nuclear and electronic excitation
along the trajectory of the ions, and to embed
simultaneously an additional element. An advantage of
this synthesis is the formation of an amorphous layer on
fabricated products in a controlled way, by choosing the
incident particle and its energy. Although the Zr-based
glassy alloys are attractive due to high glass-forming ability,
the ion beam effects on Zr-based alloy have been
investigated mainly in the binary system such as Zr-Fe, or
using swift heavy ions concerning extremely large electronic
energy deposition. Recently we demonstrated that the ion
irradiation effects on the primary precipitates during heat
2) 3)
treatment and the ion-beam induced amorphization of the
Zr-Cu-Ni-Al alloy. In this study, nano-crystalline formation
and its effects on the mechanical properties were examined in
Zr-Cu-Ni-Al amorphous alloy irradiated by ion beams.
The samples used in the present study were metallic glass
ribbons of Zr55Ni5Cu30Al10 prepared by the melt spinning
method and were amorphous films of Zr65Ni10Cu17.5Al7.5 deposited on NaCl substrate by the RF magnetron sputtering
method. Some selected samples were prepared to thin foils
using focused ion beam (FIB) technique. A master alloy
was produced by arc melting method using 99.99 mass% Zr,
99.999 mass% Cu, 99.999mass% Al and 99.99 mass% Ni
under purified Ar atmosphere. The crystal structure of the
sample surface was investigated by X-ray diffractometry
(XRD) with Cu-Kα radiation using a glancing incident angle
α of 0.5 – 1.0 degree. Ions of Mg, P, and Bi with the 200 –
500 keV were implanted into the sample at room
temperature. The structural and compositional changes of
the ion implanted surface were investigated by transmission
electron microscope (TEM), X-ray diffractometry (XRD)
and Rutherford Backscattering Spectrometry (RBS).
Figure 1 shows bright-filed TEM images and selected
area diffraction patterns of Zr55Al10Ni5Cu30 films. Because
the calculated mean projected range of the 250 keV P ions
was about 180 nm, most of the incident ions penetrated the
film of 100 nm thick. For the un-implanted sample, the
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SAD pattern has wide halo rings without spots, while the
bright-field TEM image shows a typical columnar
characteristic of the microstructure of about 100 nm width.
Nano-crystalline precipitates of fcc-Zr 2Cu were effectively
formed with a size of 5 – 20 nm in the amorphous matrix by
ion irradiation to fluences above 1 × 1016 cm -2 , although the
long-range ordering of the structure was not observed in the
X-ray diffraction patterns. The size and the concentration
of the ion-induced precipitates were increased with the
nuclear energy deposition of the ion, and the structure of the
precipitates was independent of the ion species. No other
capable structure of the precipitates, such as bct-Zr 2Cu,
fcc-Zr 2Ni and Zr 6Al 2Ni, was observed. The hardness and
elastic modulus estimated by the nano-indentation were
proportional to the volume fraction of the ion-induced
precipitates.
References
1) A. Inoue, Acta Mater. 48 (2000) 279.
2) S. Nagata et al., Nucl. Instrum. Meth. B 257 (2007) 420.
3) S. Nagata et al., Nucl. Instrum. Meth. B 267 (2009)
1514.
Fcc-Zr2Cu
250 keV P +
4 × 10 16 cm -2
Fig. 1 Bright-filed TEM micrographs and selected area
diffraction patterns of Zr 55Al 10Ni 5Cu 30 films; (a) as
prepared, (b) irradiated by 250 keV P + to 5 × 1015 cm -2 ,
(c) irradiated by 250 keV P + to 4 × 1016 cm -2 ,
(d) irradiated by 250 keV P + to 4 × 1016 cm -2 .