US 4,109,374 AGranted

Superconductor composite and method of making the same

AssigneeAluminum Company of America

InventorsClayton N. Whetstone, Douglas A. Koop, James D. Dowd

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Abstract

A selectively constituted stabilized multiple element or cell superconductor composite comprising a plurality of cores of stabilizing material with each of the cores surrounded by a tube of superconducting material in intimate contact therewith and a matrix body of normally conductive material surrounding and intimately contacting the superconducting metal tubes, thereby separating each tube from other tubes in the superconductor composite. The stabilized superconductor composite is formed by mechanically reducing a composite body of matrix material, tubes and cores simultaneously. The various materials in the composite are selected to balance properties so as to facilitate the working thereof into the desired final size and configuration.

Claims25

Dependent claims

A method of producing a worked superconductor composite comprising a plurality of individually stabilized superconductor elements in a normally resistive matrix, said method comprising the steps of

(1) providing a composite working stock comprising an aluminum alloy matrix metal said alloy consisting essentially of at least 1% of alloying additions selected from the group consisting of up to 3% Si, up to 6% Cu, up to 2% Mn, up to 10% Mg, up to 10% Zn, up to 0.5% Cr, up to 2% Fe, Ni or Co, balance substantially aluminum and incidental elements and impurities, said aluminum alloy matrix having a substantially high electrical resistivity of 10.sup.-7 ohm-cm or more at superconducting temperatures said aluminum alloy matrix metal being in the form of workable stock, said aluminum alloy matrix metal having situated therewithin a plurality of spaced substantially parallel elongate tubes of a workable metal superconducting at superconducting temperatures and, situated within said elongate tubular superconductor tubes, stabilizing cores of substantially pure aluminum having an electrical resistivity of 10.sup.-8 ohm-cm or less and substantially greater than the superconductor tubes but substantially less than the matrix metal at superconducting temperatures, the respective metals for said matrix and superconductor tubular members being selected such that the initial ratio of the flow stress between superconductor and matrix is 8 or less which said flow stress ratio is maintainable at said level of 8 or less substantially throughout metal working operations whereby the superconductor tubes and matrix are laminarly co-reducible by metal working operations:
(2) subjecting said composite working stock to at least one metal working procedure to reduce its cross-sectional area and elongate its length to a substantial extent, said working procedure being conducted so as to favor laminar flow conditions and maintain said flow stress ratio at said level of 8 to 1 or less to uniformly co-reduce said composite stock and each member within said composite stock to provide a superconducting composite body having said stabilizing core members, said superconductor tubular members and said resistive matrix all substantially proportionally reduced in cross sectional size and intimately bonded together.

A method of forming a worked superconductor composite comprising the steps of

(1) providing composite working stock comprising:
(a) a matrix composed of an aluminum base alloy consisting essentially of 4 to 6% magnesium and 0.05 to 0.25% each of manganese and chromium, balance essentially aluminum, said matrix alloy having an electrical resistivity of at least 10.sup.-7 ohm-cm at superconducting temperatures,
(b) a plurality of elongate superconductor tubular members situated in spaced substantially parallel relationship within said matrix, said superconductor members being in an alloy consisting essentially of 40 to 60% niobium, balance essentially titanium, said alloy being workable to decrease its cross section and elongate its length,
(c) stabilizing cores situated within said elongate tubular superconductor members and consisting essentially of high purity aluminum having an electrical resistivity of not greater than 10.sup.-8 ohm-cm and substantially less than said matrix at superconducting temperatures,
(d) said matrix having a flow stress such that the flow stress ratio of superconductor to matrix is 8 or less and is maintainable substantially throughout metal working operations;
(2) encapsulating said composite working stock within a readily workable aluminum alloy can having at one end a substantially tapered conical substantially solid metal portion, said can being substantially evacuated and hermetically sealed;
(3) extruding said encapsulated composite working stock by urging it, conical portion first, through a laminar flow die having a relatively shallow draft angle and radii at each end thereof, the entrance radius being at least twice the exit radius to provide extruded composite stock;
(4) further working said extruded working stock by drawing such through a plurality of progressively decreasing dies to a reduction of at least 50%;
(5) annealing said stock;
(6) further drawing said stock to an additional reduction of at least 50%;
(7) precipitation heat treating said stock so as to effect in said superconductor portions thereof precipitation of constituent phases from solution thereby to enhance its superconductive properties by heating the composite to a temperature of about 500.degree. to 1000.degree. F.;
(8) thereafter further drawing said stock to a reduction of at least 30% in cross-sectional area to produce a superconductor composite wire in a strain hardened condition;
(9) subjecting said wire to a thermal treatment at a temperature of about 200.degree. to 300.degree. F. substantially anneal and relieve work hardening effects in said core member and enhance its stabilizing characteristics while retaining substantial amounts of strain hardening effects in said matrix and said superconductor tubes.

10 more elements

Dependencies are inferred from the claim text.