21-25 July 2019
Connecticut Convention Center, Level 6
US/Eastern timezone

M1Or2A-05: Workability and recrystallization behavior of Nb-Ta, and Nb-Ta-Hf alloys

22 Jul 2019, 12:00
15m
Level 6, Room 12-13

Level 6, Room 12-13

Contributed Oral Presentation M1Or2A - A15 Conductors

Speaker

Benjamin Walker (Department of Mechanical Engineering)

Description

Recent advances in Nb3Sn to meet the very demanding FCC specification of Jc greater than 1500A/mm2 (4.2K, 16T) has led to the development of an Nb-Ta-Hf alloy, which has indicated high layer Jc’s of 3700A/mm2 are possible. This high Jc translates to a non-Cu Jc of 2200A/mm2 in an RRP® configuration. The reason for this high Jc (16T,4.2K) is because the irreversibility field of (Nb-Ta)3Sn is unaffected due to the additions of Hf to an Nb-Ta alloy and due to the formation of ultra-fine grain (UFG) Nb3Sn. The mechanism of formation of UFG Nb3Sn is intricately related to microstructure in the Nb-Ta-Hf alloy during the reaction heat treatment stages. To realize the promise of Hf additions, and make a magnet conductor workability of Nb-Ta-Hf up to large strains needs investigation. In this study we investigate the workability of Nb-Ta-Hf restack multi-filaments to true strains beyond 10, and compare them with the base Nb-Ta alloy. Given the relevance of the microstructure in the alloy rod during the Nb3Sn reaction we also compare the recrystallization behavior of the heavily drawn Nb-Ta, and Nb-Ta-Hf conductors. Results of multi-filament conductor drawing have been performed up to a strain of 7, and no intermediate breaks have been observed. Recrystallization behavior of Nb-Ta-Hf alloy at a strain of 7 indicates significant grain growth occurs only beyond 750°C, whereas grain growth is observed at 600°C in the corresponding Nb-Ta conductors.

Primary authors

Benjamin Walker (Department of Mechanical Engineering) Dr Shreyas Balachandran (National High Field Magnet Laboratory) William L. Starch (National High Magnetic Field Laboratory, Florida State University) Peter Lee (Florida State University) Chiara Tarantini (FSU) David Larbalestier (National High Magnetic Field Laboratory)

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