IMPROVEMENT IN THE CHARACTERISTICS OF TERNARY NIOBIUM TITANIUM TANTALUM ALLOYS

IN RECENT YEARS SEVERAL INVESTIGATIONS HAVE BEEN CARRIED OUT ON NIOBIUM TITANIUM TANTALUM (NBTITA) TERNARY ALLOYS, AND THE CRITICAL CURRENT (JC) RESULTS HAVE NOT BEEN SUFFICIENTLY SUPERIOR TO THE BINARY ALLOY AT EITHER 4.2 K OR 1.8 K TO WARRANT LARGE SCALE DEVELOPMENT. RECENT WORK, HOWEVER HAS SHOWN THE REASONS FOR THIS. THE ALLOYS CHOSEN DID NOT HAVE THE HIGHEST UPPER CRITICAL FIELDS (HC2S) AND CRITICAL TEMPERATURES (TCS) AND THE HEAT TREATMENTS USED DID NOT APPEAR TO BE IDEAL FOR MAXIMUM PINNING. THE PHASE I PROJECT WILL CARRY OUT THREE PARALLEL INVESTIGATIONS: (1) A MODIFIED HEAT TREATMENT SCHEDULE WILL BE APPLIED TO THE MULTIFILAMENTARY 25 WT. % TA, WT. % TI ALLOY TO IMPROVE THE SIZE AND DISTRIBUTION OF THE PRECIPITATE. THIS SHOULD IMPROVE THE JC PROPERTIES IN THE MEDIUM FIELD RANGE, (2) AN ALLOY ALREADY SELECTED ON THE BASIS OF HIGHER HC2 AND TC AT 4.2 K WILL BE PROCESSED INTO SMALL BILLETS OF A MULTIFILAMENTARY MATERIAL AND ITS PROPERTIES COMPARED WITH THE TWO ALLOYS ALREADY FABRICATED IN A SIMILAR MANNER, AND (3) AN ALLOY WHICH SHOWS MAXIMUM HC2 AT 2 K AND A REASONABLY HIGH TC WILL ALSO BE PURCHASED AND PROCESSED INTO MONOFILAMENTARY MATERIAL AND THE TC AND HC2 DETERMINED IN THIS FORM. IN PHASE II ONE OR TWO ALLOYS WHICH SHOW PROMISE WILL BE MADE INTO FULL SIZED MULTIFILAMENTARY BILLETS AND THEIR PROPERTIES DETERMINED.