CEC-ICMC 2015 - Timetable, Abstracts and Presentations

Investigation of structural and critical parameters changings after heat treatment of thin NbTi cold-rolled foil with anisotropic pinning

Not scheduled

2h

JW Marriott Starr Pass Resort

Poster Presentation ICMC-01 - NbTi/Nb3Sn/A15 Processing and Properties

Speaker

Mr Sergey Shavkin (NRC "Kurchatov Institute", Moscow, Russia)

Description

It is well known that in NbTi alloys the α-Ti nanostructure demonstrates pinning force anisotropy regarding magnetic field and Lorentz force directions. The investigation of such anisotropy is more appreciable using thin foil than round wires due to the absence of axial averaging. Earlier [1] we described the results of detailed study and developed the model of the critical current anisotropy in cold-rolled Nb50wt%Ti foil with the thickness of 10 μm where the main pinning appears due to the grain boundaries structure of elongated flat grains. Now we present the results of the correlations between the structure changes, corresponding pinning force anisotropy and critical parameters in cold-rolled Nb50%wtTi thin foil after heat treatment of 385ºC during 25 hours. Detailed TEM and SEM investigation were performed on the scanning/transmission electron microscope Titan 80-300 and EDX energy dispersive X-ray microanalysis system. The phase and texture analysis were performed using Bruker D8 Discover diffractometer and high resolution diffraction measurements on the beamline of Kurchatov synchrotron radiation source in transmission geometry where 2D detector is used. Texture analysis demonstrated complicated combined texture of β-phase with FWHM of 5º along foil rolling direction. Texture does not change after heat treatment. The lattice parameter increases from 3.289A to 3.295A, the lattice micro-distortion decreases from 0.74% to 0.60%. The critical temperature increases from 8.86K to 9.00K. The content of α-Ti increases from 1.5%wt to 8%wt. The α-Ti particles are quite large (up to 300 nm) and located mainly on β-phase grain boundaries. The variations of the pinning force anisotropy are discussed in frames of abovementioned changings of pinning system caused by heat treatment. 1. E.Yu.Klimenko, S.V.Shavkin, P.V.Volkov, JETPh, 85(3), 573-587 (1997)