FABRICATION OF A SUPERCONDUCTING SUPER COLLIDER DIPOLE MAGNET BORE TUBE LINER FROM COPPER-NIOBIUM NANOCOMPOSITE PRODUCED BY MECHANICAL ALLOYING

A NEED EXISTS AT THE SUPERCONDUCTING SUPER COLLIDER LABORATORY (SSCL) FOR A HIGH STRENGTH, MODERATE CONDUCTIVITY COPPER BASED ALLOY OR COMPOSITE FOR POSSIBLE APPLICATION AS A BORE TUBE LINER FOR THE DIPOLE MAGNETS. THE EFFECTIVENESS OF THE TUBE IN THIS APPLICATION IS A FUNCTION OF THE MATERIAL'S RESISTIVITY AND THE WALL THICKNESS OF THE TUBE. THIS RESULTS IN A NARROW RANGE OF ACCEPTABLE RESISTIVITIES. IF THE MATERIAL IS TOO CONDUCTIVE THE WALL THICKNESS MUST BE REDUCED TO THE POINT WHERE THE WALL IS SO THIN THAT IT MAY NOT SURVIVE THE FORCES GENERATED DURING A MAGNET QUENCH. MOST COMMERCIALLY AVAILABLE COPPER ALLOYS ARE EITHTER TOO RESISTIVE OR NOT RESISTIVE ENOUGH AT THE REQUIRED STRENGTH LEVELS. HOWEVER, COPPER-NIOBIUM (CUNB) NANOCOMPOSITE DOES POSSES THE DESIRED STRENGTH/RESISTIVITY COMBINATION. WHILE THE HIGHEST STRENGTHS HAVE BEEN REPORTED IN WIRE DRAWN COMPOSITES, THIS FORM IS INAPPROPRIATE FOR A NUMBER OF POTENTIAL APPLICATIONS SUCH AS THE ABOVE BORE TUBE LINER BECAUSE OF THE VERY LARGE COLD WORK STRAINS THAT MUST BE APPLIED TO THE MATERIAL TO DEVELOP ITS HIGH STRENGTH. A MORE FLEXIBLE METHOD OF PROCESSING WHICH WILL ALLOW MATERIAL TO BE PRODUCED IN MORE USABLE SHAPES WHILE RETAINING, OR EXCEEDING, THE STRENGTH OBSERVED IN WIRE DRAWN MATERIALS IS DESIRED. MECHANICAL ALLOYING WILL BE EMPLOYED IN AN EFFORT TO DEVELOP THE REQUIRED PROPERTIES IN THE DESIRED PRODUCT FORM. THIS SHOULD PRODUCE A PRODUCT POSSESSING THE REQUIRED PROPERTIES IN THE AS-EXTRUDED CONDITON ELIMINATING THE NEED FOR EXTENSIVE COLD WORK STRAIN. ALSO, BECAUSE OF THEIR NANOMETER SCALE MICROSTRUCTURE THE NIOBIUM DISPERSOIDS WILL RESIST COARSENING AT ELEVATED TEMPERATURES SO THAT THE STRENGTH OF THE PRODUCT WILL BE NEGLIBIBLY EFFECTED BY HIGH TEMPERATURE OPERATIONS SUCH AS BRAZING. THE OBJECTIVE OF PHASE I IS TO DEMONSTRATE THAT ITS NANOCRYSTALLINE MICROSTRUCTURE WILL IMPART ANOMALOUSLY HIGH STRENGTHS IN THE AS-EXTRUDED CONDITION. AN EVALUATION OF THE COMPOSITE'S SUITABILITY FOR SSC BORE TUBE LINER APPLICATIONS WILL BE CONDUCTED. THE PHASE II OBJECTIVE IS TO RESOLVE ANY REMAINING TECHNICAL ISSUES AND SCALE-UP THE PROCESS TO PRODUCES BORE TUBE LINER SECTIONS FOR MAGNET QUENCH TESTING AT SSCL.