A cold worked multifilamentary Cu/Nb-47w%Ti wire was annealed at a temperature of 375°C for various times from 2 minutes up to 100 hours. Filaments were extracted from copper matrix by etching. With the attempt to improve understanding of superconducting properties, extracted filaments were tested with a Vibrating Sample Magnetometer (VSM) as a function of field over a wide temperature range. The Ic curves were obtained from the magnetization cycles at different temperatures, and the normalized pinning forces (fp) were plotted as a function of the reduced applied field (b). For each sample, it was found that the fp peak clearly shifts to lower fields as the temperature approaches Tc. Further, the pinning curves also depended on the annealing time. The fp vs. b curves were reproduced with the 2-components model which recently has been developed and successfully validated on a number of optimized NbTi commercial strands. Results are discussed in terms of current pinning models, also in comparison with results of microstructural characterization. © 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Guest Editors.
Evolution of the pinning force of NbTi filaments as a function of isothermal annealing time
Muzzi, L.;De Marzi, G.;
2012-01-01
Abstract
A cold worked multifilamentary Cu/Nb-47w%Ti wire was annealed at a temperature of 375°C for various times from 2 minutes up to 100 hours. Filaments were extracted from copper matrix by etching. With the attempt to improve understanding of superconducting properties, extracted filaments were tested with a Vibrating Sample Magnetometer (VSM) as a function of field over a wide temperature range. The Ic curves were obtained from the magnetization cycles at different temperatures, and the normalized pinning forces (fp) were plotted as a function of the reduced applied field (b). For each sample, it was found that the fp peak clearly shifts to lower fields as the temperature approaches Tc. Further, the pinning curves also depended on the annealing time. The fp vs. b curves were reproduced with the 2-components model which recently has been developed and successfully validated on a number of optimized NbTi commercial strands. Results are discussed in terms of current pinning models, also in comparison with results of microstructural characterization. © 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Guest Editors.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
