National Institute for Materials Science

National Research Institute for Metals

Inter-university Research Institute Corporation High Energy Accelerator Research Organization

Takao Takeuchi

Nobuya Banno

Kyoji Tachikawa

Toshihisa Asano

Kiyoshi Inoue

Yasuo Iijima

Kazuhiko Nakagawa

Kazumasa Togano

Akihiro Kikuchi

Hitoshi Wada

Kiyosumi Tsuchiya

Michio Kosuge

Problem There is proposed an innovative cross-sectional structure, with an idea contrary to the conventional one, utilizing the non-reactivity between Cu and Ta (or between Ag and Nb, Ta) in a high-temperature short-time heat treatment, thus achieving (1) the suppression of the low magnetic-field instability, (2) excellent wire drawability of a precursor wire, and (3) the reduction of the cost required for the incorporation of a stabilizer. Means for Resolution There is proposed a structure having an assembly of a plurality of single wires, wherein the assembly is covered with an outer cover (skin) formed from Nb or Ta, wherein each of the single wires has an Nb/Al composite filament region which is formed from a composite of Nb and Al mixed in an Nb:Al molar ratio of 3:1, and which is covered with a partition formed from Nb or Ta, and further covered with an interfilamentary barrier formed from Cu or Ag disposed around the partition.

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A composite barrier-type NbAl superconducting multifilament wire material comprises Nb barrier filaments, Ta barrier filaments, Nb bulk dummy filaments, and a Nb or Ta covering. In the composite barrier-type NbAl superconducting multifilament wire material, the Nb barrier filaments and Ta barrier filaments are disposed in the wire material so that the Nb barrier filaments are concentrated in a filament region near a core formed from the Nb bulk dummy filaments and only the Ta barrier filaments are disposed or the Nb barrier filaments are dispersed in the Ta barrier filaments in an outer layer portion formed from a region outside the Nb barrier filaments, excluding the Nb or Ta covering.

Composite barrier-type Nb3AI superconducting multifilament wire material

A composite multi-core wire rod in which a plurality of Al alloy wires containing 15 at % to 40 at % of Ge are arranged in Nb matrix at a core diameter of 2 &#x3bc;m to 20 &#x3bc;m is subjected to heating for at least five hours at a temperature ranging from 1300&#xb0; C. to 1600&#xb0; C.; and additionally heating at a temperature ranging from 650&#xb0; C. to 900&#xb0; C.

A superfine multi-core NbAl superconductive wire is produced by getting a NbAl superconductive wire ready which was obtained by subjecting a precursor wire having a superfine multi-core structure in which a plurality of Nb/Al complex cores are embedded in Nb, Ta, a Nb based dilute alloy, or a Ta based dilute alloy as the matrix to a rapid heating and quenching treatment comprising rapidly heating to a temperature range near 2,000&#xb0; C. in 2 seconds,

This invention provides a production method of Nb Al superconducting multifilamentary wire based on rapid-heating, quenching and transformation method, capable of producing a high-performance Nb Al superconducting multifilamentary wire by improving critical temperature thereof, upper critical field and critical current density. Upon a first stage heat treatment of beating a composite, in which bcc phase Nb&mdash;Al supersaturated solid solution is dispersed in Nb matrix, the bcc phase Nb&mdash;Al supersaturated solid solution ordered in temperature rise process is made disordered at an initial phase thereof and a non-reacting portion located adjacent is heated using a reaction heat generated when transforming this disordered bcc phase to A15 phase. Then, disordering of the bcc phase is promoted while propagating a high-temperature transformation region so as to automatically progress high-temperature beat treatment. As a result, a reaction-transformation is caused to block stacking fault from being generated in the A15 phase and crystal grain from being coarse and then, a second stage heat treatment for improving a long range ordering of the A15 phase is carried out.

Production method of Nb3Al superconducting multifilamentary wire

A long, linear composite article which is characterized in that a large number of composite filaments are present as spaced from one another in a continuous layer composed of copper, a copper alloy, niobium, tantalum or vanadium, each of said composite filaments having a structure that at least one strand of a linear body is surrounded by an aluminum alloy or niobium, said linear body being composed substantially of extremely fine, filamentary superconducting Nb.sub.3 Al compound having an average diameter of from about 0.03 .mu.m to about 1 .mu.m. The said composite article can be prepared by drawing a composite material composed of (a) an aluminum alloy and (b) niobium, together with copper or a copper alloy once or plural times repeatedly, until the average diameter of the aluminum alloy of (a) becomes about 1 .mu.m or less, and heat-treating the resultant linear composite material. This composite articles exhibit excellent superconducting characteristics in high-magnetic field and alternating-current magnetic field.

Multifilament Nb.sub.3 Al superconducting linear composite articles

In a method for producing an Nb.sub.3 Sn superconductor which comprises elongating a composite composed of a core portion of an alloy containing niobium and a matrix portion of a copper-tin alloy, a copper-tin-aluminum alloy or a copper-tin-gallium alloy and heat-treating the elongated composite to form an Nb.sub.3 Sn layer between the core portion and the matrix portion; the improvement wherein the core portion of the composite is made of a niobium-titanium alloy containing 0.1 to 10 atomic percent of titanium.

Method for producing Nb.sub.3 Sn superconductors

In a method for producing a Nb.sub.3 Sn superconductor which comprises drawing a composite having a core of a Nb-Hf alloy containing 0.1 to 30 atomic % of Hf and a sheath containing Cu and Sn, and heat-treating the composite to form a Nb.sub.3 Sn layer between the core and the sheath; the improvement wherein the sheath is formed of pure Cu, a Cu-Sn alloy containing not more than 6 atomic % of Sn, a Cu-Ga alloy containing not more than 20 atomic % of Ga, a Cu-Al alloy containing not more than 20 atomic % of Al, a Cu-Ga-Sn alloy containing not more than 6 atomic % of Sn and not more than 20 atomic % of Ga, or a Cu-Al-Sn alloy containing not more than 6 atomic % of Sn and not more than 20 atomic % of Al; and after the drawing, a Sn film is coated on the surface of the sheath, and then the product having a Sn film coated thereon is heat-treated.

Growing community of inventors

Ibaraki, Japan

Takao Takeuchi