Author: Nicometo, E.M.
Paper Title Page
SUPCAV002 Ex-Situ Investigation of the Effects of Heating Rate on the Recrystallization in Rolled Polycrystals of High-Purity Niobium 1
  • Z.L. Thune, N. Fleming, C. McKinney, E.M. Nicometo
    MSU, East Lansing, Michigan, USA
  • S. Balachandran
    NHMFL, Tallahassee, Florida, USA
  • T.R. Bieler
    Michigan State University, East Lansing, Michigan, USA
  Funding: US Dept. of Energy award DE-SC0009960
The consistent production of high-purity niobium cavities for superconducting radiofrequency (SRF) applications is crucial for enabling improvements in accelerator performance. Recent work has shown that dislocations and grain boundaries trap magnetic flux which dissipates energy and degrades cavity performance. We hypothesize that the current heating rate used in production is too slow and therefore facilitates recovery rather than recrystallization. Recovery, unlike recrystallization, does not reduce the number of geometrically necessary dislocations (GNDs) that are strongly correlated to trapped magnetic flux. Using excess high-purity niobium saved from the production of a cavity, the material was divided into two groups and rolled to ~30% reduction with half rolled parallel to the original rolling direction, and the other half rolled perpendicular. To examine the effect of heating rate, samples were encapsulated in quartz tubes and placed into either a preheated furnace or a cold furnace to allow for heat treatments at different rates. Then using ex-situ electron backscatter diffraction (EBSD) mapping, the extent of recrystallization was determined.
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About • Received ※ 22 June 2021 — Revised ※ 31 August 2021 — Accepted ※ 16 November 2021 — Issue date ※ 20 February 2022
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