Abstract: In a method of producing a superconducting Nb.sub.3 Sn wire which comprises passing a wire or tape of a niobium-base alloy through a molten metal bath containing tin and then heat-treating it to form a Nb.sub.3 Sn compound layer on the surface of said wire or tape, the improvement wherein said niobium-base alloy is an alloy comprising niobium and 0.1 to 30 atomic percent of hafnium, and said molten metal bath is a molten bath of pure tin or a tin-base alloy consisting of tin, from 0.1 to 70 atomic percent of one element of Group IIIb of the periodic table selected from the group consisting of gallium, indium, and aluminum, and from 0.1 to 70 atomic percent of one element of Group Ib of the periodic table selected from the group consisting of copper and silver, the total amount of the element of Group IIIb and the element of Group Ib not exceeding 70 atomic percent.

Abstract: A method for producing a V.sub.3 Al superconductor which comprises making a composite composed of a sheath portion of a copper alloy containing 1 to 15 atomic percent of germanium, 1 to 15 atomic percent of silicon or 2 to 25 atomic percent of gallium and surrounded by the sheath portion, at least one core portion of a vanadium-aluminum alloy containing 0.5 to 20 atomic percent of aluminum; elongating the composite; and then heat-treating the elongated composite thereby to form a V.sub.3 (Al, Ge), V.sub.3 (Al, Si) or V.sub.3 (Al, Ga) layer between the sheath portion and the core portion.

Abstract: In a method for producing V.sub.3 Ga superconductors which comprises forming a composite of a core portion and a sheath portion surrounding said core portion, said sheath portion being composed of a gallium-containing alloy selected from the group consisting of copper-gallium and copper-silver-gallium alloys, and said core portion being composed of a vanadium metal, elongating said composite, and heat-treating the resulting elongated composite to form a V.sub.3 Ga layer between said sheath and core portions; the improvement wherein the gallium-containing alloy has a gallium content of 0.1 to 30 atomic percent and additionally contains at least one metal selected from the group consisting of 0.05 to 5 atomic percent of magnesium, 0.5 to 10 atomic percent of aluminum, 0.1 to 10 atomic percent of cerium and 0.05 to 10 atomic percent of sodium, and the vanadium metal is a vanadium alloy containing 0.1 to 15 atomic percent of gallium.

Abstract: In a method for producing Nb.sub.3 Sn superconductors which comprises forming a composite consisting of a core portion and a sheath portion surrounding said core portion, said sheath portion being composed of a Cu-Sn alloy, and said core portion being composed of a Nb metal; elongating said composite; and heat-treating the resulting elongated composite to form an Nb.sub.3 Sn layer between said sheath and core portions; the improvement wherein the Cu-Sn alloy contains 1 to 20 atomic percent of Sn and the Nb metal is an Nb alloy containing 0.1 to 30 atomic percent of Hf.

Abstract: A superconductor including V.sub.3 Ga is produced by making a composite of a vanadium core metal, a continuous portion of aluminum surrounding the vandium core metal or forming a second core, and a copper, silver or copper-silver alloy containing gallium, fabricating the composite to the desired shape, and heat-treating the shaped composite. The vanadium core may contain titanium, zirconium or hafnium, and the continuous portion of aluminum may contain copper or zirconium.

Abstract: A superconductor including V.sub.3 Ga is produced by making a composite of a vanadium core metal, a continuous portion of aluminum surrounding the vanadium core metal or forming a second core, and a copper, silver or copper-silver alloy containing gallium, fabricating the composite to the desired shape, and heat-treating the shaped composite. The vanadium core may contain titanium, zirconium or hafnium, and the continuous portion of aluminum may contain copper or zirconium.