The crystal structure of (Nb0.75Cu0.25)Sn2 in the Cu-Nb-Sn system

Martin, Stefan; Walnsch, Alexander; Nolze, Gert; Leineweber, Andreas; Léaux, F.; Scheuerlein, C.

doi:10.1016/j.intermet.2016.09.008

Cited by 16 publications

(9 citation statements)

References 27 publications

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“…They also found that 'long lasting plateaus are counterproductive to J c ' [27] in high-Sn content internal-tin wires like RRP ® , because such wires are susceptible to the formation of Nausite. As it will be shown below, and as suspected in [27,28], this Nausite phase (the Sn-Nb-Cu ternary phase discovered by Naus et al [29] in 2002, and now identified as Nb 0.75 Cu 0.25 Sn 2 [30]) is the source of Nb dissolution and subsequent coarsegrain A15 formation, which were important suspects for the J c degradation in RRP ® wires. A row of this coarse-grain A15 derived from Nausite can be seen in fractured A15 layer in figure 5 at the inner wall of the A15 ring (bottom of image).…”

Section: Recent Studies Of Cu-sn Mixingmentioning

confidence: 80%

Controlling Cu–Sn mixing so as to enable higher critical current densities in RRP^®Nb₃Sn wires

Sanabria¹,

Field²,

Lee³

et al. 2018

Supercond. Sci. Technol.

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Dipole magnets for the proposed Future Circular Collider (FCC) demand specifications significantly beyond the limits of all existing Nb 3 Sn wires, in particular a critical current density (J c ) of more than 1500 A mm −2 at 16 T and 4.2 K with an effective filament diameter (D eff ) of less than 20 μm. The restacked-rod-process (RRP ® ) is the technology closest to meeting these demands, with a J c (16 T) of up to 1400 A mm −2 , residual resistivity ratio>100, for a subelement size D s of 58 μm (which in RRP ® wires is essentially the same as D eff ). An important present limitation of RRP ® is that reducing the sub-element size degrades J c to as low as 900 A mm −2 at 16 T for D s =35 μm. To gain an understanding of the sources of this J c degradation, we have made a detailed study of the phase evolution during the Cu-Sn 'mixing' stages of the wire heat treatment that occur prior to Nb 3 Sn formation. Using extensive microstructural quantification, we have identified the critical role that the Sn-Nb-Cu ternary phase (Nausite) can play. The Nausite forms as a well-defined ring between the Sn source and the Cu/Nb filament pack, and acts as an osmotic membrane in the 300°C-400°C rangegreatly inhibiting Sn diffusion into the Cu/Nb filament pack while supporting a strong Cu counter-diffusion from the filament pack into the Sn core. This converts the Sn core into a mixture of the low melting point (408°C) η phase (Cu 6 Sn 5 ) and the more desirable ε phase (Cu 3 Sn), which decomposes at 676°C. After the mixing stages, when heated above 408°C towards the Nb 3 Sn reaction, any residual η liquefies to form additional irregular Nausite on the inside of the membrane. All Nausite decomposes into NbSn 2 on further heating, and ultimately transforms into coarse-grain (and often disconnected) Nb 3 Sn which has little contribution to current transport. Understanding this critical Nausite reaction pathway has allowed us to simplify the mixing heat treatment to only one stage at 350°C for 400 h which minimizes Nausite formation while encouraging the formation of the higher melting point ε phase through better Cu-Sn mixing. At a D s of 41 μm, the Nausite control heat treatment increases the J c at 16 T by 36%, reaching 1300 A mm −2 (i.e. 2980 A mm −2 at 12 T), and moving RRP ® closer to the FCC targets.

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Section: Recent Studies Of Cu-sn Mixingmentioning

confidence: 80%

Controlling Cu–Sn mixing so as to enable higher critical current densities in RRP^®Nb₃Sn wires

Sanabria¹,

Field²,

Lee³

et al. 2018

Supercond. Sci. Technol.

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“…Despite decades of research on growing Nb3Sn in Cu-Nb-Sn composite wires (often with the addition of Ti or Ta), knowledge of the thermodynamics of this system is incomplete. This is exemplified by the observation of the ternary phase nausite (Nb0.75Cu0.25Sn2) [10], which is not present in the evaluated phase diagram. TU Bergakademie Freiberg is contributing to the FCC Study with a detailed investigation of phase equilibria in the Cu-Nb-Sn system, with particular emphasis on the temperature range of relevance to superconducting wires.…”

Section: B Thermodynamics and Phase Transformations In The Cu-nb-sn mentioning

confidence: 92%

The CERN FCC Conductor Development Program: A Worldwide Effort for the Future Generation of High-Field Magnets

Ballarino

Hopkins

Bordini

et al. 2019

IEEE Trans. Appl. Supercond.

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The study of next generation high energy accelerators based on 16 T dipoles has emphasized the need for higher performance, cost-effective Nb3Sn superconducting wires. A Conductor Development Program aiming to reach a non-copper critical current density (Jc) of 1500 A/mm 2 at 16 T and 4.2 K has been launched by CERN, with the involvement of industry and laboratories worldwide. In this article, the targets and strategy of the program are presented, with an overview of the wire layouts and development activities being pursued by each partner, and the latest characterization results are reported. Three of the four participating manufacturers have successfully reached the first stage Jc milestone, but a significant advance is still needed to achieve the final target. The next steps are briefly discussed, as the program focuses increasingly on novel alloys and methods to maximize Jc.

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“…During production of superconducting magnets the following phases are expected: Nb 3 Sn, Cu 6 Sn 5 , Cu 3 Sn, Cu and Nb . However, investigating high‐energy synchrotron XRD experiments (ID15A beamline at ESRF, Grenoble) some minor peaks could not be assigned to one of these phases.…”

Section: Lattice Parameter Determinationmentioning

confidence: 99%

“…Although the result is less accurate than desired, the Bravais‐lattice type as well as the lattice parameters derived by EBSD were the key indication to focus on transition‐metal distannides with hexagonal symmetry and similar lattice parameters. Based on this assumption the lattice parameters and the crystal structure data have been successfully refined .…”

Section: Lattice Parameter Determinationmentioning

confidence: 99%

See 1 more Smart Citation

Electron backscatter diffraction beyond the mainstream

Nolze

Hielscher

Winkelmann

2016

Crystal Research and Technology

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We present special applications of electron backscatter diffraction (EBSD) which aim to overcome some of the limitations of this technique as it is currently applied in the scanning electron microscope. We stress that the raw EBSD signal carries additional information which is useful beyond the conventional orientation determination. The background signal underlying the backscattered Kikuchi diffraction (BKD) patterns reflects the chemical composition and surface topography but also contains channeling-in information which is used for qualitative real-time orientation imaging using various backscattered electron signals. A significantly improved orientation precision can be achieved when dynamically simulated pattern are matched to the experimental BKD patterns. The breaking of Friedel's rule makes it possible to obtain orientation mappings with respect to the point-group symmetries. Finally, we discuss the determination of lattice parameters from individual BKD patterns. Subgrain structure in a single quartz grain. The increased noise level in the left map reflects the lower precision of a standard orientation determination using band detection by the Hough transform. The right map results from the same experimental raw data after orientation refinement using a pattern matching approach. The colors correspond an adapted inverse pole figure color key with a maximum angular deviation of about 2 • from the mean orientation.

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The crystal structure of (Nb0.75Cu0.25)Sn2 in the Cu-Nb-Sn system

Cited by 16 publications

References 27 publications

Controlling Cu–Sn mixing so as to enable higher critical current densities in RRP^®Nb₃Sn wires

Controlling Cu–Sn mixing so as to enable higher critical current densities in RRP^®Nb₃Sn wires

The CERN FCC Conductor Development Program: A Worldwide Effort for the Future Generation of High-Field Magnets

Electron backscatter diffraction beyond the mainstream

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The crystal structure of (Nb0.75Cu0.25)Sn2 in the Cu-Nb-Sn system

Cited by 16 publications

References 27 publications

Controlling Cu–Sn mixing so as to enable higher critical current densities in RRP®Nb3Sn wires

Controlling Cu–Sn mixing so as to enable higher critical current densities in RRP®Nb3Sn wires

The CERN FCC Conductor Development Program: A Worldwide Effort for the Future Generation of High-Field Magnets

Electron backscatter diffraction beyond the mainstream

Contact Info

Product

Resources

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Controlling Cu–Sn mixing so as to enable higher critical current densities in RRP^®Nb₃Sn wires

Controlling Cu–Sn mixing so as to enable higher critical current densities in RRP^®Nb₃Sn wires