Effects of Grain Size and Interstitial Content on Recrystallization in Nb after Cold Rolling

Bennett IV, Thomas J.; Taleff, Eric M.; Dhakal, Pashupati; Balachandran, Shreyas; Lee, Peter J.; Bieler, Thomas R.; Eisenlohr, Philip

doi:10.1109/TASC.2025.3538673

Effects of Grain Size and Interstitial Content on Recrystallization in Nb after Cold Rolling

Journal Article · Fri Aug 01 00:00:00 EDT 2025 · IEEE Transactions on Applied Superconductivity

DOI:https://doi.org/10.1109/TASC.2025.3538673· OSTI ID:2568393

Bennett IV, Thomas J. ^[1]; Taleff, Eric M. ^[1]; Dhakal, Pashupati ^[2]; Balachandran, Shreyas ^[2]; Lee, Peter J. ^[3]; Bieler, Thomas R. ^[4]; Eisenlohr, Philip ^[4]

Univ. of Texas, Austin, TX (United States)
Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Laboratory (MagLab)
Michigan State Univ., East Lansing, MI (United States)

A fully recrystallized microstructure with a fine grain size can improve the performance of superconducting radio-frequency (SRF) cavities produced from high-purity Nb (ASTM B393–18 Type 5 Nb) while providing mechanical strength. Recrystallization depends on impurity content, initial microstructure, deformation state, and annealing conditions. To better understand how fine-grained, fully recrystallized microstructures may be produced, the recrystallization behaviors of Type 5 and Type 2 Nb materials were studied. Type 5 Nb specimens were produced with both fine and coarse initial grain sizes. All were cold rolled and then annealed under vacuum for one hour to determine the rolling reductions and temperatures required for recrystallization. The recrystallized fraction exceeded 95% in fine-grained Type 5 Nb rolled to a 30% or greater thickness reduction and then annealed at 800 °C or higher. The coarse grained Type 5 Nb required greater rolling reductions to produce any recrystallized grains at 800 °C. The higher interstitial content of the Type 2 Nb required a temperature of 1000 °C or higher to reach a recrystallized fraction greater than 95% in specimens rolled to a 60% reduction. Recrystallization is more easily achieved during annealing at a given temperature for a set time by increasing rolling reduction, decreasing interstitial content, and decreasing initial grain size prior to cold rolling. In conclusion, to avoid grain growth following recrystallization, which increases grain size, the minimum time and temperature necessary for complete recrystallization should be applied.

Research Organization:: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Nuclear Physics (NP); USDOE Office of Science (SC), High Energy Physics (HEP); National Science Foundation (NSF)

Grant/Contract Number:: AC05-06OR23177; SC0009960

OSTI ID:: 2568393

Report Number(s):: JLAB-ACC--25-4331; DOE/OR/23177--7859

Journal Information:: IEEE Transactions on Applied Superconductivity, Journal Name: IEEE Transactions on Applied Superconductivity Journal Issue: 5 Vol. 35; ISSN 1051-8223; ISSN 2378-7074; ISSN 1558-2515

Publisher:: IEEECopyright Statement

Country of Publication:: United States

Language:: English

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