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Microstructures and Hydrogen Permeability of Nb-NiTi Eutectic Alloys Prepared by Directional Solidification

Published online by Cambridge University Press:  26 February 2011

Yuji Yamaguchi ,
Kyosuke Kishida ,
Sho Tokui ,
Kazuhiro Ishikawa ,
Katsushi Tanaka ,
Kiyoshi Aoki  and
Haruyuki Inui
Yuji Yamaguchi
Affiliation:
yuuji.yamaguchi@t02.mbox.media.kyoto-u.ac.jp, Kyoto University, Department of Materials Science and Engineering, Sakyo-ku, Kyoto, 606-8501, Japan, +81-75-753-5473, +81-75-753-5461
Kyosuke Kishida
Affiliation:
k.kishida@materials.mbox.media.kyoto-u.ac.jp, Kyoto University, Department of Materials Science and Engineering, Sakyo-ku, Kyoto, 606-8501, Japan
Sho Tokui
Affiliation:
mms05008@std.kitami-it.ac.jp, Kitami Institute of Technology, Department of Materials Science, 165 Koen-cho, Kitami, 090-8507, Japan
Kazuhiro Ishikawa
Affiliation:
ishikazu@mail.kitami-it.ac.jp, Kitami Institute of Technology, Department of Materials Science, 165 Koen-cho, Kitami, 090-8507, Japan
Katsushi Tanaka
Affiliation:
k.tanaka@materials.mbox.media.kyoto-u.ac.jp, Kyoto University, Department of Materials Science and Engineering, Sakyo-ku, Kyoto, 606-8501, Japan
Kiyoshi Aoki
Affiliation:
aokiky@mail.kitami-it.ac.jp, Kitami Institute of Technology, Department of Materials Science, 165 Koen-cho, Kitami, 090-8507, Japan
Haruyuki Inui
Affiliation:
haruyuki.inui@materials.mbox.media.kyoto-u.ac.jp, Kyoto University, Department of Materials Science and Engineering, Sakyo-ku, Kyoto, 606-8501, Japan
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Abstract

The Nb-NiTi eutectic alloys were directionally solidified (DS) in an optical floating zone furnace. Columnar grains of eutectic structures containing rod-shaped Nb in the NiTi matrix is observed in the DS ingots irrespective of the alloy composition. Well-aligned rod-type eutectic microstructures can be obtained for samples with a composition of Nb-41Ni-40Ti grown at relatively slow growth rates below 2.5mm/h. The hydrogen permeability along the direction parallel to the Nb rods of Nb-41Ni-40Ti DS alloy grown at 1mm/h is 2.60×10-8mol H2 m-1 Pa-1/2 at 673K, which is over 20 times higher than that measured perpendicular to the Nb-rod direction. No hydrogen embrittlement is observed between 573 and 673K indicating that the eutectic structure itself is favorable in suppressing the hydrogen embrittlement of Nb.

Keywords

directional solidificationmicrostructurepurification
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 980: Symposium II – Advanced Intermetallic-Based Alloys , 2006 , 0980-II05-52
Copyright
Copyright © Materials Research Society 2007

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References

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