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Multifilamentary Nb3Sn by an Improved External Diffusion Method

  • S. F. Cogan
  • D. S. Holmes
  • J. D. Klein
  • R. M. Rose
Part of the Cryogenic Materials Series book series (CRYMS)

Abstract

The external diffusion technique permits easy mechanical fabrication of Nb3Sn-based superconducting multifilamentary composites due to the lower work-hardening rate of Cu compared to Cu-Sn bronze. However, Kirkendall porosity can appear to a disastrous extent in external diffusion composites rather than the lesser degree apparent in internal diffusion products.1 Figure 1 shows a cross section of the extremely fragile material resulting from the application of the external diffusion technique to multi filamentary composites with no precautions taken to suppress Kirkendall porosity. Figure 2 shows the vastly improved cross section resulting from the incorporation of a solution preanneal prior to electroplating in the external diffusion method. This approach was developed in our laboratory2 upon recognition of the heterogeneous nucleation mechanism in the observed Kirkendall porosity. The heterogeneously nucleated voids precipitate from the temporary supersaturation of lattice vacancies caused by the differing diffusion mobilities of copper and tin in the copper matrix. The nucleation substrates are mainly particles of oxide, tarnish, or other foreign matter adherent to the surfaces of the original composite components or included in the copper itself.

Keywords

Critical Current Density Fibre Size External Diffusion Nb3Sn Layer Fragile Material 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. 1.
    D. S. Easton and D. M. Kroeger, IEEE Trans. Magn. MAG-15: 178 (1979).Google Scholar
  2. 2.
    S. F. Cogan, D. S. Holmes, and R. M. Rose, Appl. Phys. Letters 35: 557 (1979).CrossRefGoogle Scholar
  3. 3.
    A. Smigelskas and E. Kirkendall, Trans. AIME 171: 130 (1947).Google Scholar
  4. 4.
    S. F. Cogan, D. S. Holmes and R. M. Rose, to appear in J. Appl. Phys., August 1980.Google Scholar
  5. 5.
    S. F. Cogan and R. M. Rose, to appear in Cryogenics.Google Scholar
  6. 6.
    H. H. Farrell, G. H. Gilmer, and M. Suenaga, J. Appl. Phys. 45: 4025 (1974).CrossRefGoogle Scholar

Copyright information

© Plenum Press, New York 1980

Authors and Affiliations

  • S. F. Cogan
    • 1
  • D. S. Holmes
    • 1
  • J. D. Klein
    • 1
  • R. M. Rose
    • 1
  1. 1.Department of Materials Science and EngineeringMassachusetts Institute of TechnologyCambridgeUSA

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