Ternary Nb-Ti-Ta Alloys for High Field 2 K Applications--Alloy Selection and Process Optimization

76065-Even before Nb3Sn dipole magnets are ready to come on line, particle accelerators for high energy physics will require higher performance NbTi alloy superconductors for operation above 8 tesla. Although yielding excellent 5 T properties, the composition of contemporary NbTi, as well as their associated precipitation heat treatments (PHT), actually are optimal for high-field operation. Furthermore, for high fields, even better performance is obtainable with the Ta-substituted ternary alloy NbTiTa. This project will demonstrate the exceptional high field properties of some NbTiTa compositions. In Phase I, NbTiTa alloys will be selected and melted, and monofilamentary NbTiTa/Cu composite strands will be produced and heat treated (prior to the final cold deformations stages) so as to optimize ?-phase precipitation (for flux pinning, hence Jc) and ?-matrix composition (for Hc2). In order to administer to the strand the usual ¿commercial¿ overall strain during the overall diameter reduction, a cycle of Equal Channel Angle Extrusion (strain without area reduction) will be inserted into the small-scale process. Finally, the superconducting properties will be verified. Commercial Applications and Other Benefits as described by the awardee: High Energy Physics will be the primary beneficiary of this program. The technology should lead to the production of higher performance NbTi-base alloy superconductors for operation above 8 tesla, and to the manufacture of superconducting cables for use in improved focusing quadrupoles and the ¿low field¿ graded windings of higher field dipoles.