On the formation of voids in internal tin Nb3Sn superconductors

Scheuerlein, C.; Michiel, Marco Di; Haibel, Astrid

doi:10.1063/1.2716346

Cited by 36 publications

(42 citation statements)

References 7 publications

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“…Our ex situ XMT results show long pores at the end of the 575°C dwell and also at the end of the entire heat treatment, with a longer duration and a higher temperature than those investigated by Scheuerlein et al, who performed in situ synchrotron XMT during heat treatment [17,18,20], but both results, though using wires of different design, are in good agreement. All void volumes presented here were converted to percentages of the respective non-Cu volume for ease of comparison.…”

Section: Titanium Additionsupporting

confidence: 74%

“…The morphology and amount of voids towards the end of the heat treatment closely resemble those at the point where liquid formation occurred (refer to Fig. 2 in [20] and Fig. 9 below).…”

Section: Titanium Additionmentioning

confidence: 60%

“…All void volumes presented here were converted to percentages of the respective non-Cu volume for ease of comparison. The results show pore volume percentage of 0.895% (HT1, end of 575°C dwell), 0.640% (HT1, end of reaction) and 0.528% (HT2, end of 575°C dwell), 0.448% (HT2, end of reaction); compared to Scheuerlein's 2.61% at maximum void volume and 0.616-0.703% at 540°C [20] (Fig. 9).…”

Section: Titanium Additionmentioning

confidence: 88%

“…The former are inevitable, as there is a density difference between different phases formed, most noteworthy being the shrinkage associated with the formation of the dense e phase, and the 37% expansion upon formation of the superconducting A15-phase Nb 3 Sn. It can be observed from the results of the elegant work done by Haibel and Scheuerlein et al using synchrotron XMT to follow a single sample during a simplified heat treatment [20], that many of the pores formed during the solid-phase transformations will eventually be closed while those as a result of liquid-phase formation remain.…”

Section: Titanium Additionmentioning

confidence: 99%

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Microstructure development in Nb3Sn(Ti) internal tin superconducting wire

Pong

Hopkins

et al. 2008

J Mater Sci

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The authors have studied the phase formation sequences in a Nb 3 Sn 'internal tin' process superconductor. Heat treatments were performed to convert the starting materials of tin, Ti-Sn, copper and niobium, to bronze and Nb 3 Sn. Specimens were quenched at different points of the heat treatment, followed by metallography to identify the phases present and X-ray microtomography (XMT) to investigate the void volume and distribution. An unexpected observation of the microstructure development was the uphill diffusion of tin during the Cu-Sn reactive diffusion. Some defects likely to affect the superconducting performance of the wires were observed. Microscopy revealed the presence of a Ti-Sn intermetallic compound displacing the niobium filaments, and XMT revealed the formation of long pores in the longitudinal direction. Two types of pore formation mechanism, in addition to Kirkendall pores, are proposed. The phase and microstructure development suggests that low-temperature heat treatment (below 415°C) will have significant influence on optimising the final superconducting properties.

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Section: Titanium Additionsupporting

confidence: 74%

“…The morphology and amount of voids towards the end of the heat treatment closely resemble those at the point where liquid formation occurred (refer to Fig. 2 in [20] and Fig. 9 below).…”

Section: Titanium Additionmentioning

confidence: 60%

Section: Titanium Additionmentioning

confidence: 88%

Section: Titanium Additionmentioning

confidence: 99%

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Microstructure development in Nb3Sn(Ti) internal tin superconducting wire

Pong

Hopkins

et al. 2008

J Mater Sci

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“…The formation of voids in internal tin Nb 3 Sn wires has been studied recently by synchrotron micro tomography and x-ray diffraction. 30 A different interpretation of the observed phenomenon could be that the critical current remains reversible as long as the variation in the Nb 3 Sn lattice parameters with applied axial strain stays linear ͑elastic regime͒. For a similar jack- Further observations can be inferred from experimental data.…”

Section: Discussionmentioning

confidence: 89%

Improvement of electromechanical properties of an ITER internal tin Nb3Sn wire

Mondonico

Seeber

Senatore

et al. 2010

Journal of Applied Physics

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The critical current of an internal tin Nb 3 Sn wire developed by Oxford Instruments, Superconducting Technology for International Thermonuclear Experimental Reactor ͑ITER͒ ͑OST type-I, billet No. 7567͒ has been studied under axial strain at fields between 12 and 19 T at 4.2 K. Simulating the situation in a cable in conduit, where thermally induced compressive strain is important, a single wire ͑strand͒ was jacketed with AISI 316L stainless steel. The reinforced wire shows an important increase in m , the applied strain where I c reaches its maximum, from 0.25% to 0.57%. In addition the irreversibility limit, irr , is improved from 0.50% applied strain to Ͼ1.10%. It could also be shown that the I c at zero intrinsic strain is almost identical. This demonstrates that jacketing does not influence the physical parameters of the original wire. Experimental data of the bare wire has been well fitted by different strain functions. However, it was not possible to model the data of the jacketed wire. There are indications that only models which take into account the multidimensional character of strain are able to describe the behavior but further development is required.

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In‐Situ Synchrotron X‐Ray Microtomography Studies of Microstructure and Damage Evolution in Engineering Materials

Beckmann¹,

Grupp

Haibel

et al. 2007

Adv Eng Mater

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In materials science X‐ray microtomography has evolved as an increasingly utilized technique for characterizing the 3D microstructure of materials. The fundamentals of X‐ray microtomography experimental methods and the reconstruction and data evaluation processes are briefly described. A review of in‐situ synchrotron X‐ray microtomography studies in literature is given. Examples of recent work include in‐situ microtomography investiagtions of metallic foams, in‐situ studies of the sintering of copper particles, and in‐situ investigations of creep damage evolution in composites. Future perspectives of in‐situ X‐ray microtomography studies in materials science are outlined.

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On the formation of voids in internal tin Nb3Sn superconductors

Cited by 36 publications

References 7 publications

Microstructure development in Nb3Sn(Ti) internal tin superconducting wire

Microstructure development in Nb3Sn(Ti) internal tin superconducting wire

Improvement of electromechanical properties of an ITER internal tin Nb3Sn wire

In‐Situ Synchrotron X‐Ray Microtomography Studies of Microstructure and Damage Evolution in Engineering Materials

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