Solid-State Diffusion Formation of Nanocrystalline Nb3Sn Layers at Two-Staged Annealing of Multifilamentary Nb/Cu-Sn Wires

2012 ◽  
Vol 16 ◽  
pp. 69-75 ◽  
Author(s):  
E.N. Popova ◽  
I.L. Deryagina ◽  
E.P. Romanov ◽  
E.A. Dergunova ◽  
A.E. Vorobyova ◽  
...  
Keyword(s):  
Diffusion Annealing ◽  
Solid State Diffusion ◽  
Superconducting Layer ◽  
Superconducting Wires ◽  
Second Stage ◽  
State Diffusion ◽  
Columnar Grains ◽  
Average Size ◽  
Bronze Matrix ◽  
Active Formation

The structure of Nb3Sn-based, bronze-processed Ti-doped multifilamentary superconducting wires has been studied by TEM and SEM after the first (5750C,100 h) and the second (6500C,100 h) stage of the diffusion annealing. The Nb3Sn layers formation in all the composites proceeds by one and the same mechanism and starts with nucleation of particles and very fine grains of this phase in Nb filaments where Sn diffuses from the bronze matrix. Ti, inserted both in the bronze matrix, or Nb filaments, diffuses into the growing superconducting layer and promotes its more active formation. At the first stage of annealing (5750C, 100 h) Nb3Sn grains have an average size of 40 nm, and at the second stage (6500C, 100 h) they increase by a factor of 1.5 and the grain size distribution gets wider. After the two-stage annealing the amount of the residual niobium is small, and some Nb filaments, especially in doped composites, almost completely transform into Nb3Sn. In the Nb3Sn layers of a zone of columnar grains is adjacent to the residual Nb.

Transverse sections of multifilamentary Nb3Sn superconductor wires in TEM

1978 ◽  
Vol 36 (1) ◽  
pp. 148-149
Author(s):  
Edward F. Koch
Keyword(s):  
Heat Treatment ◽  
Thermal Stability ◽  
Carrying Capacity ◽  
Flux Pinning ◽  
Diffusion Method ◽  
Solid State Diffusion ◽  
Superconducting Wires ◽  
Hexagonal Shape ◽  
Heat Treated ◽  
State Diffusion

New devices using fine multifilament superconducting wires are becoming more important, since these wires now have better thermal stability, lower losses and better current carrying capacity. The multifilament Nb3Sn superconductor wires reviewed in this report were made by the solid state diffusion method developed by Kaufman and Pickett. In this process, a niobium rod in a bronze jacket is extruded into an hexagonal shape, this rod is then cut into lengths, which are packed together in a bronze jacted and extruded again. This process is continued until the total reduction ratio for the niobium is a billion to one. At this point the wires are still ductile and can be fabricated into their final shape. The Nb2-bronze composite is then heat treated, and the tin from the bronze diffuses into the Nb, forming Nb3Sn. This heat treatment is important, since it controls both the amount of Nb3Sn formed and the grain size, which affects flux-pinning.

Morphology and Structure of Nb3Sn Diffusion Layers in Superconductors with Tubular Nb Filaments

2015 ◽  
Vol 364 ◽  
pp. 139-146
Author(s):  
Elena N. Popova ◽  
I.L. Deryagina ◽  
E.I. Patrakov ◽  
E.G. Valova-Zaharevskaya
Keyword(s):  
Electron Microscopy ◽  
Diffusion Annealing ◽  
Structure And Morphology ◽  
Diffusion Layers ◽  
Morphology And Structure ◽  
Columnar Grains ◽  
Equiaxed Grains ◽  
Complete Transformation ◽  
Bronze Matrix

The structure and morphology of Nb3Sn layers in superconducting Nb/Cu-Sn composites with ring (tubular) Nb filaments have been studied by transmission (TEM) and scanning (SEM) electron microscopy after various regimes of diffusion annealing. It is demonstrated that the tubular geometry of Nb filaments, in which Sn diffuses from the bronze matrix both from inside and outside, ensures practically complete transformation of Nb into the superconducting Nb3Sn phase. Besides, at certain regimes of the diffusion annealing this geometry enables the improvement of the superconducting layers morphology compared to that of wires with continuous filaments, namely, to obtain wide Nb3Sn layers with fine equiaxed grains and to avoid the formation of columnar grains, which promotes enhanced current-carrying capacities of the wires.

Joining of Ti3SiC2 with Ti–6Al–4V Alloy

2002 ◽  
Vol 17 (1) ◽  
pp. 52-59 ◽  
Author(s):  
N.F. Gao ◽  
Y. Miyamoto
Keyword(s):  
Solid State ◽  
Rate Constant ◽  
Liquid State ◽  
Parabolic Rate Constant ◽  
Diffusion Path ◽  
Solid State Diffusion ◽  
Diffusion Controlled ◽  
State Diffusion ◽  
Rate Controlled ◽  
Higher Temperature

The joining of a Ti3SiC2 ceramic with a Ti–6Al–4V alloy was carried out at the temperature range of 1200–1400 °C for 15 min to 4 h in a vacuum. The total diffusion path of joining was determined to be Ti3SiC2/Ti5Si3Cx/Ti5Si3Cx + TiCx/TiCx/Ti. The reaction was rate controlled by the solid-state diffusion below 1350 °C and turned to the liquid-state diffusion controlled with a dramatic increase of parabolic rate constant Kp when the temperature exceeded 1350 °C. The TiCx tended to grow at the boundarywith the Ti–6Al–4V alloy at a higher temperature and longer holding time. TheTi3SiC2/Ti–6Al–4V joint is expected to be applied to implant materials.

Investigation of the diffusion behavior in Sn-xAg-yCu/Cu solid state diffusion couples

2016 ◽  
Vol 686 ◽  
pp. 794-802 ◽  
Author(s):  
Yuan Yuan ◽  
Dajian Li ◽  
Yuanyuan Guan ◽  
Hans J. Seifert ◽  
Nele Moelans
Keyword(s):  
Solid State ◽  
Solid State Diffusion ◽  
Diffusion Couples ◽  
Diffusion Behavior ◽  
State Diffusion
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