Recent progress on improvement to mechanical properties of DI-BSCCO wire

To improve the mechanical properties of silver-sheathed BSCCO wire, the laminated BSCCO wires with stainless steel were made under some experimental conditions. The dependence of the stainless steel thickness and the dependence of the pre-tension of stainless steel tapes on the laminated BSCCO were investigated by mechanical tests (tensile test at 77 K and RT and double-bending test at RT) using short samples. Due to the difference of the coefficient of thermal expansion (CTE) and the relaxation to equilibrium after removing the total pre-tension of no laminated BSCCO (insert tape) and stainless steel tapes, the residual axial compressive strain applies to an insert tape after the lamination process. A high compressive strain up to the compressive yield of the silver-alloy is so useful for improvement of the mechanical properties of BSCCO wire. Measurement results were approximately the same as the simple model calculated from the residual strain applied to an insert tape by the difference of CTE and pre-tension. The stainless-steel-laminated BSCCO wire 'Type HT-SS' has been able to be achieved over 500 MPa at 77 K by increasing stainless steel thickness and the residual axial compression for an insert tape. The developed tough DI-BSCCO has a higher hoop force to compare with YBCO-coated conductor using Hastelloy substrates under the same circumstances such as magnetic field, winding diameter and transport current. (paper)