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Title: Direct observation of dislocation structure evolution in SRF cavity niobium using electron channeling contrast imaging

Abstract

Two major goals of superconducting radio frequency cavity research and development are achieving higher accelerating gradient and gaining the highest quality factor, a measure of efficiency. However, the consistent improvement of these performance metrics is restricted by many factors, one of which is microstructural defects, such as dislocation substructures within the material. In this work, dislocation evolution is compared in four samples extracted from a 2.8 mm thick large-grain niobium slice, with tensile axes chosen to generate specific dislocation structures during subsequent deformation. The four samples are (1) as-extracted, (2) extracted and annealed, (3) extracted and then deformed to 40% tensile strain, and (4) extracted, annealed at 800 °C 2 h, and then deformed to 40% strain. Electron channeling contrast imaging was performed on all samples to characterize initial dislocation density and dislocation structure evolution due to annealing and deformation, and related to the mechanical behavior observed in stress-strain curves. A fundamental understanding of dislocation evolution in niobium is necessary to develop computational models to simulate cavity forming, which could enable new processing methods for cavity fabrication to be identified that could lead to improved performance.

Authors:
 [1];  [1];  [1]
  1. Michigan State Univ., East Lansing, MI (United States)
Publication Date:
Research Org.:
Michigan State Univ., East Lansing, MI (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1611273
Alternate Identifier(s):
OSTI ID: 1478278
Grant/Contract Number:  
SC0009962
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 124; Journal Issue: 15; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Physics; Crystallographic defects; Projective geometries; Plasticity; Deformation; Computational models; Transition metals; Electrical properties and parameters; Metallurgy; Stress strain relations

Citation Formats

Wang, M., Kang, D., and Bieler, T. R. Direct observation of dislocation structure evolution in SRF cavity niobium using electron channeling contrast imaging. United States: N. p., 2018. Web. doi:10.1063/1.5050032.
Wang, M., Kang, D., & Bieler, T. R. Direct observation of dislocation structure evolution in SRF cavity niobium using electron channeling contrast imaging. United States. doi:10.1063/1.5050032.
Wang, M., Kang, D., and Bieler, T. R. Sun . "Direct observation of dislocation structure evolution in SRF cavity niobium using electron channeling contrast imaging". United States. doi:10.1063/1.5050032. https://www.osti.gov/servlets/purl/1611273.
@article{osti_1611273,
title = {Direct observation of dislocation structure evolution in SRF cavity niobium using electron channeling contrast imaging},
author = {Wang, M. and Kang, D. and Bieler, T. R.},
abstractNote = {Two major goals of superconducting radio frequency cavity research and development are achieving higher accelerating gradient and gaining the highest quality factor, a measure of efficiency. However, the consistent improvement of these performance metrics is restricted by many factors, one of which is microstructural defects, such as dislocation substructures within the material. In this work, dislocation evolution is compared in four samples extracted from a 2.8 mm thick large-grain niobium slice, with tensile axes chosen to generate specific dislocation structures during subsequent deformation. The four samples are (1) as-extracted, (2) extracted and annealed, (3) extracted and then deformed to 40% tensile strain, and (4) extracted, annealed at 800 °C 2 h, and then deformed to 40% strain. Electron channeling contrast imaging was performed on all samples to characterize initial dislocation density and dislocation structure evolution due to annealing and deformation, and related to the mechanical behavior observed in stress-strain curves. A fundamental understanding of dislocation evolution in niobium is necessary to develop computational models to simulate cavity forming, which could enable new processing methods for cavity fabrication to be identified that could lead to improved performance.},
doi = {10.1063/1.5050032},
journal = {Journal of Applied Physics},
number = 15,
volume = 124,
place = {United States},
year = {2018},
month = {10}
}

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