DEVELOPMENT OF A LOW COST METHOD FOR THE FABRICATION OF FINE FILAMENT NIOBIUM-TITANIUM CONDUCTOR

FABRICATION OF THE MAGNETS FOR THE SUPERCONDUCTING SUPER COLLIDER (SSC) WILL NECESSITATE THE PURCHASE OF THOUSANDS OF TONS OF FINE-FILAMENT NIOBIUM-TITANIUM (NBTI) WIRE. FORGED NBTI INGOTS ARE CURRENTLY UTILIZED IN THE MANUFACTURE OF THIS WIRE. SUBSTANTIAL SAVINGS IN RAW MATERIAL AND PROCESSING COSTS COULD BE REALIZED IF AS-CAST NBTI INGOT COULD BE USED IN PLACE OF FORGED INGOT. HOWEVER, AS-CAST INGOTS CONTAIN VERY LARGE GRAINS CAPABLE OF PENETRATING FILAMENT DIFFUSION BARRIERS AS THE MONOFILAMENT AND MULTIFILAMENT COMPOSITES ARE WORKED DOWN. LOCALIZED BARRIER THINNING WILL OCCUR UNDER THESE CIRCUMSTANCES, RESULTING IN COPPER-TITANIUM INTERMETALLIC FORMATION IN THESE REGIONS DURING PRECIPITATION HEAT TREATMENT OF THE MULTIFILAMENT WIRE. THIS INTERMETALLIC CAUSES FILAMENT SAUSAGING AND SEVERE CURRENT DENSITY DEGRADATION DURING SUBSEQUENT WIRE REDUCTION. THIS PROJECT EVALUATES AN APPROACH TO AVOIDING THE BARRIER PENETRATION PROBLEM BY WRAPPING THE AS-CAST NBTI INGOT WITH FINE-GRAINED NBTI SHEET TO PRESENT A SMOOTH PROFILE TO THE DIFFUSION BARRIER. IN PHASE I, PURCHASED CAST INGOTS WILL BE WRAPPED WITH NBTI SHEET (FORGED AND ROLLED). THIS ASSEMBLY WILL BE WORKED AND THEN EVALUATED.