CONTINUOUS EXTRUSION OF NB3SN SUPERCONDUCTORS

THE PUSH FOR HIGHER FIELD MAGNETS FOR APPLICATIONS SUCH AS FUSION MACHINES HAS DRIVEN THE SEARCH FOR A COST-EFFECTIVE, RELIABLE MANUFACTURING PROCESS FOR HIGH FIELD, HIGH CURRENT DENSITY SUPERCONDUCTORS. THE DESIGN/PROCESS CHOICES THAT THE MANUFACTURER OF FILAMENTARY COMPOSITES MUST MAKE USUALLY REQUIRE A COMPROMISE BETWEEN CURRENT DENSITY AND PIECE LENGTH. THE REQUIREMENTS FOR SUPERCONDUCTOR PERFORMANCE, FOR EXAMPLE THE HIGHLY DEFORMED MICROSTRUCTURES IN NBTI COMPOSITES OR THE VERY DIFFERENT MECHANICAL PROPERTIES OF THE COMPONENTS IN NB3SN COMPOSITES, PLACE STRINGENT RESTRICTIONS ON THE AREA REDUCTION PROCESS. WIRE DRAWING IS COST-EFFECTIVE BECAUSE IT CAN BE DONE SEMICONTINUOUSLY; HOWEVER, THE HIGH TENSILE FORCES INVOLVED ARE NOT IDEAL FOR PROCESSING COMPOSITES WITH WIDELY DIFFERING COMPONENTS. CONVENTIONAL EXTRUSION HOLDS THE ADVANTAGES OF LARGE AREA REDUCTION AND COMPRESSIVE FORCES, BUT IS SEVERELY LIMITED IN PIECE LENGTH, HENCE MUST BE DONE AT LARGE DIAMETERS. A HIGHLY PROMISING ALTERNATIVE APPEARS TO BE A CONTINUOUS EXTRUSION PROCESS THAT ALLOWS LARGE AREA REDUCTIONS USING COMPRESSIVE FORCES, SMALL STARTING DIAMETERS, AND UNLIMITED LENGTHS. THIS STUDY WILL EXPLORE THE FEASIBILITY OF CONTINUOUS EXTRUSION OF DISTRIBUTED SN NB3SN COMPOSITES, A DEMANDING MATERIAL TO PROCESS BECAUSE OF THE USE OF PURE TIN ALONG WITH NIOBIUM AND COPPER. THE EFFECTS OF THE EXTRUSION RATIO, EXTRUSION RATE, DIE ANGLE, AND LUBRICANT ON THE FILAMENT QUALITY, METALLURGICAL BONDING, AND SUBSEQUENT DRAWABILITY OF THE COMPOSITE WILL BE STUDIED.