低温工学
Online ISSN : 1880-0408
Print ISSN : 0389-2441
ISSN-L : 0389-2441
Nb3Al線材化プロセスはどのように発展してきたか
井上 廉
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1998 年 33 巻 9 号 p. 604-613

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Nb3Al with stoichiometric composition shows Tc above 19K and Hc2 (4.2K) above 30T, much higher than in commercially available Nb-Ti wire and Nb3Sn wire. Therefore the developments of fabrication processes for Nb3Al conductors were performed early on with zeal, but ended without success because stoichiometric Nb3Al is unstable at any temperatures except about 2, 000°C. Moreover, the fabrication speed of Nb3Al through solid-state diffusion reaction is very slow. To overcome these difficulties, a recent new process, RHQT (rapid-heat, quench, and transformation), was developed for fabricating Nb3Al multifilamentary conductors with near-stoichiometric composition and fine-grained crystals. Through this process we have succeeded in the fabrication of Nb3Al multifilamentary wires showing 2 to 5 times larger Jc at 4.2K than those of commercialized superconductors in any field, and their Tc of about 17.6K and Hc2 (4.2K) of about 26T are similar to those of the (Nb, Ti)3Sn wire. Furthermore, excellent tolerance to mechanical strain is also obtained for the Nb3Al conductor. I believe the new Nb3Al conductor should soon be commercialized and take the place of Nb3Sn conductor. In this paper I would like to describe the historical progress in the Nb3Al conductor fabrication process up to the birth of the RHQT process.

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