NIOBIUM-TITANIDE TIN/COPPER MULTIFILAMENTARY SUPERCONDUCTING WIRE WITH NIOBIUM/TITANIUM COMPOSITE FILAMENTS

THE ACCELERATOR, FUSION, AND NUCLEAR MAGNETIC RESONANCE (NMR) PROJECTS IN THE FIELD OF APPLIED SUPERCONDUCTIVITY ALL REQUIRE NEW HIGH-FIELD SUPERCONDUCTING WIRES THAT HAVE HIGHER CURRENT-CARRYING CAPABILITY IN HIGHER MAGNETIC FIELDS. UP TO NOW, NIOBIUM TIN (NB3SN) IS THE MOST IMPORTANT PRACTICAL SUPERCONDUCTOR FOR HIGH-FIELD APPLICATIONS. ONE OF THE EFFECTIVE APPROACHES TO RAISE THE CRITICAL CURRENT DENSITIES OF NB3SN IN HIGH MAGNETIC FIELDS IS TO ALLOY NB3SN WITH TITANIUM (TI) OR TANTALUM (TA). THE CURRENT PRACTICE OF ADDING TI INTO NB3SN IS TO USE NBTI ALLOY RODS AND/OR COOPER (CU) BRONZE MATRIX ALLOYED WITH TI TO ASSEMBLE THE MONOCORE BILLETS. NEVERTHELESS, THE PROCESSING OF THESE CONDUCTORS OFTEN SUFFERS FROM DRAWABILITY PROBLEMS DUE TO ENHANCED WORK HARDENING. PHASE I WILL INVESTIGATE THE FEASIBILITY OF DEVELOPING A TERNARY (NB,TI)3SN/CU MULTIFILAMENTARY SUPERCONDUCTING WIRE WITH NB/TI COMPOSITE FILAMENTS PREPARED FROM PURE NB AND TI SHEETS USING A JELLY-ROLL TECHNIQUE. IT HAS BEEN DEMONSTRATED THAT LONG LENGTHS OF NBTI SUPERCONDUCTOR WITH ARTIFICIAL PINNING CENTERS (APC) CAN BE FABRICATED FROM PURE NB AND TI SHEETS WITHOUT PRECIPITATION HEAT TREATMENTS. IT IS EXPECTED THAT USE OF NB/TI COMPOSITE FILAMENTS VIA A JELLY ROLL TECHNIQUE WILL IMPROVE THE FABRICABILITY OF THE (NB,TI)3SN/CU SUPERCONDUCTING WIRE AND CUT THE COST. THE FINE GRAIN STRUCTURE IN NB AND TI SHEETS WILL ALSO HELP TO ENHANCE THE CRITICAL CURRENT (JC) IN LOW AND INTERMEDIATE MAGNETIC FIELDS, AND REDUCE THE FILAMENT SAUSAGING AT THE SAME TIME. IN PHASE I, TWO TERNARY (NB,TI)3SN/CU SUPERCONDUCTING WIRES, ONE CONTAINING NB/TI COMPOSITE FILAMENTS AND THE OTHER CONTAINING CONVENTIONAL NB/1-2WT.%TI ALLOY FILAMENTS, WILL BE FABRICATED USING A CONVENTIONAL BRONZE-ROUTE PROCESS. THE DRAWABILITY, JC, MAGNETIZATION (HYSTERESIS LOSS), AND MICROSTRUCTURE OF THESE TWO WIRES WILL BE MEASURED AND COMPARED. THE FURTHER OPTIMIZATION AND SCALE-UP WORK WILL BE CONDUCTED IN PHASE II.