Improvements in Superconductors

1,164,816. Making superconductors; altering physical structure. IMPERIAL METAL INDUSTRIES (KYNOCH) Ltd. 20 April, 1967 [4 May, 1966], No. 19756/66. Headings B3A and B3V. A method of making a superconductor comprises cold working a superconductor material to effect at least 10% reduction, heat treating the material at 100-500‹ C. for at least 10 minutes and further cold working and heat-treating the material at least once to effect a minimum total reduction of 95%. The material is preferably an alloy of niobium and titanium or an alloy of niobium, zirconium and titanium which may be sheathed in a non-superconductor, e.g. copper. In a preferred embodiment the alloy contains 10-60% titanium, 0-40% zirconium, 0-1500 p.p.m. oxygen, 0-2000 p.p.m. nitrogen, 0-1000 p.p.m. carbon and the balance niobium. It is preferred to have a total reduction of at least 99À9%. In an example an ingot of Nb-44Ti is forged at at least 700‹ C. and sheathed in copper. The composite is heated at 450‹ C. for half an hour to bond the alloy and the copper and cold drawn 99À82%. Two specimens are taken, the first, A, cold drawn a further 90À23% and heat-treated at 400‹ C. for an hour and the second, B, heat-treated for half an hour at 350‹ C. and cold drawn eighteen times with heattreatment between each pass. The second specimen B has agreater current density than A for the same applied field. Further examples of cold working, e.g. drawing or rolling, and the subsequent heat-treatment are given in detail in the Specification.