ADVANCED ALLOY SUPERCONDUCTOR WIRE MANUFACTURING TECHNOLOGY

TO SUPPORT LARGE CURRENTS IN MULTIFILAMENTARY SUPERCONDUCTORS BASED ON NB-TI ALLOYS, A FINE SCALE SUBSTRUCTURE IS REQUIRED WITHIN THE SUPERCONDUCTOR WIRE. TOPRODUCE SUBSTRUCTURE OF THE ORDER OF 100 , THE CONVENTIONAL MULTIFILAMENTARY SUPERCONDUCTOR FABRICATION TECHNOLOGY REQUIRES A RATHER LARGE NUMBER OF TEDIOUS PROCESSING STEPS. TYPICALLY A 5 IN. DIAMETER NB-TI ALLOY INGOT IS MECHANICALLY WORKED THROUGH EXTRUSION AND WIRE DRAWING, UNTIL 5MUM DIAMETER FILAMENTS ARE OBTAINED. THE CHEMICAL INHOMOGENEITY IN THE STARTING INGOTS THAT ARISES DUE TO SEGREGATION OF ALLOYING ELEMENTS DURING SOLIDIFICATION IS OFTEN DELETERIOUS TO THE SUPERCONDUTOR PROPERTIES. AN ALTOGETHER NEW MANUFACTURING ROUTE FOR THE PREPARATION OF MULTIFILAMENTARY SUPERCONDUCTORS IS PROPOSED,WHICH HAS THE POTENTIAL OF PRODUCING SUPERCONDUCTORS WITH IMPROVED CHARACTERISTICS, AND SIGNIFICANTLY LOWER COST. THEAPPROACH INVOLVES PREPARING CONTINUOUS SUPERCONDUCTOR FILAMENTS, TYPICALLY 40MUM THICK, DIRECTLY FROM THE MELT. SUCH THIN FILAMENTS, WHEN EXTRACTED FROM THE MELT EXPERIENCEHIGH SOLIDIFICATION RATES. THE HIGH SOLIDIFICATION RATES LEAD TO A CHEMICALLY HOMOGENEOUS MICROSTRUCTURE WITH EXTREMELY FINE GRAIN SIZES AND SUB-STRUCTURES OF THE ORDER OF 100 . THE PHASE I RESEARCH WILL ADDRESS THE FEASIBILITY OF OBTAINING DESIRABLE MICROSTRUCTURES FOR FLUX PINNING AND HIGH CRITICAL CURRENT DENSITY. THIS DEVELOPMENTWILL OBVIATE ALL THE PROCESSING STEPS REQUIRING EXTENSIVE MECHANICAL DEFORMATION. APPROACHES TO INCORPORATE THE SUPERCONDUCTOR FILAMENTS PREPARED DIRECTLY FROM THE MELT, INTO COMPOSITE WIRES WILL ALSO BE EXPLORED.