Pursuing low joint resistivity in Cu-stabilized REBa2Cu3Oδ coated conductor tapes by the ultrasonic weld-solder hybrid method

Development of a coated conductor tape joint with good quality and low joint resistivity, R-sj, in terms of transport and mechanical properties, was attempted by direct bonding at the interface of the Cu-Cu stabilizers in overlapped GdBCO CC tapes. In this study, we attempted to achieve a low R-sj by introducing hybrid joining, soldering and ultrasonic welding (UW), and its mechanism was analyzed theoretically. Coated conductor tapes were experimentally joined using various methods of soldering, UW, and combinations of the two. As a result, a much lower R-sj of about 57 n Omega.cm(2) was obtained for RCE-DR-processed GdBCO CC tape joints using the hybrid joining method. The mechanical properties of the jointed CC tapes were also evaluated at room temperature and 77 K under self-field. Load-displacement curves of joined CC tapes followed the curve of the single CC tape. Critical current and joint resistance, R-j, of hybrid-joined CC tape were retained after double bending at room temperature up to 20 mm bending diameter.