Metallurgical processes in nbti filaments as a function of isothermal annealing time

J. Somerkoski, C. Fiamozzi Zignani, G. De Marzi, L. Muzzi

Research output: Contribution to conferencePaper

4 Citations (Scopus)


In an attempt to improve understanding between pinning behaviour and underlying microstructures, results of the investigation on multifilamentary Cu/Nb-47w%Ti alloy are presented. Wire was drawn to final size without intermediate stage thermomechanical treatments. Cold worked structure was subjected to isothermal annealing at 648 K for various annealing times between 2 minutes to 100 hours. Microstructural and compositional features were studied by transmission electron microscopy, TEM, and analytical TEM equipped with EDS analyzer. The pinning behavior was monitored by the maximum volume pinning force determined using transport current measurements at 4.2 K up to 9 T. According to the present results, the average grain boundary spacing remained rather constant at 45 nm throughout all annealing times while the average grain boundary width increased from the initial dimension of 1 nm to 1.8 nm after 100 hours as a result of precipitation processes at grain boundaries. Further, distributions of the grain boundary widths changed from a sharp shape to a wider spectrum of widths. The precipitation process created titanium concentration gradients in the vicinity of the grain boundaries. As the annealing time increased, the sharp gradients became shallower and Ti concentrations as low as 35 w% Ti were observed after 40 hours. High field pinning at 9 T was associated with structures having a mean grain boundary width of 1.2 nm and titanium concentration gradients on a scale of 2.5 to 5 nm from the grain boundaries. Mid magnetic field pinning was favored by microstructures having titanium gradients on a scale of 5-10 nm and the mean width of 1.5 nm while improved low field pinning at 3 T was associated with microstructures having the mean width of 1.8 nm, shallow gradients and titanium concentrations as low as 35 w% inside of the grains.
Original languageEnglish
Publication statusPublished - 2012
Externally publishedYes
EventSuperconductivity Centennial Conference, SCC 2011 - The Hague, Netherlands
Duration: 1 Jan 2012 → …


ConferenceSuperconductivity Centennial Conference, SCC 2011
CityThe Hague
Period1/1/12 → …


All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

Cite this

Somerkoski, J., Fiamozzi Zignani, C., De Marzi, G., & Muzzi, L. (2012). Metallurgical processes in nbti filaments as a function of isothermal annealing time. Paper presented at Superconductivity Centennial Conference, SCC 2011, The Hague, Netherlands.