Tensile strength for high-temperature superconducting joints fabricated with incongruent melting

• Published in: Cryogenics (Guildford) 2020-09, Vol.110, p.103130, Article 103130
• Main Authors: Kanazawa, Shintetsu, Yanagisawa, Yoshinori
• Format: Article
• Language: English
• Subjects: Bi2223; Conductors; Critical current (superconductivity); High temperature; Lap joints; Mechanical properties; Melting; NMR; Nuclear magnetic resonance; RE123; Superconducting joint; Superconducting tapes; Superconductivity; Tensile strength; Tensile stress
• ISSN: 0011-2275; 1879-2235
• DOI: 10.1016/j.cryogenics.2020.103130

•We obtained a high tensile stress above 120 MPa in superconducting joint between RE123-coated conductors.•We also obtained a high tensile stress above 80 MPa in superconducting joint between Bi2223 tapes.•The mechanical reinforcement of junction using Ni sheet was estimated.•It is important to reduce the strain at junction to protect the critical current of joints. We recently suggested a joint method by using incongruent melting for high-temperature superconducting (HTS) wires, such as joint between RE123-coated conductors and between Bi2223 multi-filamentary tapes. It is important to obtain a suitable mechanical performance in joint to develop a persistent current HTS magnet, and this joint method with the melting is considered to have a higher tensile strength than the solid diffusion. In this study, the tensile strength of such a joint at critical current under tension was investigated toward application in a HTS magnet, such as Bi2223-NMR. We prepared two types of lap joint samples between RE123-coated conductors and between Bi2223 multi-filamentary tapes, with wrapping Ni sheets on junction (joined part in joint sample). The critical current of the samples was a similar value about 15 A at 77 K. The Ic of the samples showed a dependence on a small tension of junction below 40 MPa. With the reinforcement effect of the Ni sheet, the tensile stress tolerance of both joints that Ic of joint is reversible was higher than 90 MPa.