The effect of shape and deformation inex situMgB2–W/Fe composite wires

Kòváč, Pavol; Hušek, I; Melíšek, T; Dhallé, M.; Mûller, Martín; Ouden, A. den

doi:10.1088/0953-2048/18/5/007

Cited by 20 publications

(45 citation statements)

References 15 publications

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“…The rods were filled into Fe tubes with 10 mm outer diameter and 6 mm inner diameter, which were deformed initially by rotary swaging and than by two-axial rolling to a mono-filamentary tape of thickness (a) 0.70 mm and 0.35 mm and width (b) 3.5 mm. The so-called rectangular wire-in-tube technique (RWIT) was used for assembly of multi-filamentary tapes [15]. Six pieces of mono-filamentary tape (0.70 mm × 3.5 mm) were inserted into a rectangular Fe sheath of outer size 5.5 mm × 6.75 mm and reduced by two-axial rolling to six-filamentary tapes of thickness 1.0 mm, 0.68 mm, 0.5 mm and 0.32 mm and a constant width of 3.5 mm, which corresponds to a filament thickness (h f ) ranging from 47.6 to 12.8 µm.…”

Section: Methodsmentioning

confidence: 99%

Improvement of current density by texture andI_canisotropy in thin filament MgB₂/Fe tapes

Kòváč¹,

Hušek²,

Melíšek³

et al. 2006

Supercond. Sci. Technol.

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Thin filament MgB 2 /Fe tapes have been made by the powder-in-tube technique using a precursor powder prepared by mechanical alloying and deformed by two-axial rolling. Increasing critical current density (J c ) in a parallel external magnetic field has been measured for a reduced filament thickness up to 18.5 µm; this could be effective for future practical fine-filamentary MgB 2 conductors. This increase in J c is attributed to an apparent improvement in texture introduced by rolling. Further increase in J c with reduction of filament size is limited due to chemical reaction at the filament/Fe interface during the final heat treatment at 600 • C for 3 h. On the other hand, improved texture leads to a strong critical current anisotropy, which increases with the reduced filament thickness and temperature. High I c anisotropy can lead to an apparent reduction of the total magnet current due to the effect of the radial field component, as in the case of high temperature superconducting coils.

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Section: Methodsmentioning

confidence: 99%

Improvement of current density by texture andI_canisotropy in thin filament MgB₂/Fe tapes

Kòváč¹,

Hušek²,

Melíšek³

et al. 2006

Supercond. Sci. Technol.

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“…Between D and E, however, it degrades with the same linear dependence as during the initial part A → B. We interpret this as a re-closing of the cracks that originated from the part B → C [17]. Since the damage occurring during this initial cracking is still relatively small (∼2.5% of the total current) it appears that the cracks can still be pushed together to carry (within experimental uncertainty) the same current as the undamaged tape.…”

Section: Strain Behaviour Of Mgb 2 Conductorsmentioning

confidence: 72%

“…Recently, MgB 2 tapes produced by the ex situ powder-in-tube (PIT) process (MgB 2 powder in a metal sheath) have been measured with the U-shaped spring [17]. Figure 7 shows the strain dependence of the critical current in a four-filament tape with an aspect ratio of 4.…”

Section: Strain Behaviour Of Mgb 2 Conductorsmentioning

confidence: 99%

“…Again, the value of ε irr seems closely related to the precompression of the filaments. We use the rule of mixtures to estimate the thermal precompression of the MgB 2 filaments after cool down to 4.2 K [17]. Also the MgB 2 /metal composites presented by Kitaguchi et al [18] and Goldacker et al [19,20] are analysed in terms of thermal prestrain.…”

Section: Strain Behaviour Of Mgb 2 Conductorsmentioning

confidence: 99%

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Critical current versus strain research at the University of Twente

Eck

Laan

Dhallé

et al. 2003

Supercond. Sci. Technol.

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At the University of Twente a U-shaped spring has been used to investigate the mechanical properties of a large variety of superconducting tapes and wires. Several mechanisms are responsible for the degradation of critical current as a function of applied strain. A change in its intrinsic parameters causes a reversible critical current dependence in Nb 3 Sn. The critical current reaches a maximum at a wire-dependent tensile strain level, and decreases when this tensile strain is either released or further increased. In Bi-based tapes the critical current is virtually insensitive to tensile strain up to a sample-dependent irreversible strain limit. When this limit is exceeded, the critical current decreases steeply and irreversibly. This behaviour is attributed to microstructural damage to the filaments. This cracking of the filaments is verified by a magneto-optical strain experiment. Recent experiments suggest that in MgB 2 the degradation of critical current is caused by a change in intrinsic properties and damage to the microstructure. Magneto-optical imaging can be used to investigate the influence of applied strain on the microstructure of MgB 2 , as is done successfully with Bi-based tapes. In all these conductors the thermal precompression of the filaments plays an important role. In Nb 3 Sn it determines the position of the maximum and in Bi-based and MgB 2 conductors it is closely related to the irreversible strain limit.

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“…Outras metodologias foram desenvolvidas: a partir de filamentos de boro e vapor de magnésio (CANFIELD et al, 2001), por meio de reação de varetas de magnésio com boro em pó (IMD -Internal Magnesium Difusion) (TOGANO et al, 2008), por PICT -Continuous Powder-In-Tube (YAMAMOTO et al, 2004), ou por CTFF -Continuous Tube Forming and Filling (SUMPTION et al, 2005) e ainda por RWIT -Rectangular Wire-In-Tube Technique (KOVÁČ et al, 2005). A metodologia PIT tem sido utilizado para a fabricação de fios com vários metais utilizados como revestimento, tais como: aço inoxidável (AI) (SERQUIS et al, 2003a;SERRANO et al, 2008) (BEILIN et al, 2004), Cu (SOBRERO; MALACHEVSKY; SERQUIS, 2015), Nb-Ta/Cu/AI e Nb/Cu (GOLDACKER et al, 2001;SUMPTION et al, 2007), Fe (FLÜKIGER et al, 2003;GLOWACKI et al, 2003), Fe/AI (SOLTANIAN et al, 2002) e Nb (GROVENOR et al, 2004).…”

Section: Metodologias Para Fabricação De Fios Compósitos Supercondutounclassified

Desenvolvimento da metodologia de fabricação de um fio supercondutor de MgB2

Ribeiro¹

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The discovery of superconductivity in magnesium diboride (MgB 2) in 2001 with critical temperatute (T c) of 39 K and upper critical magnetic field (H c2) (H ⊥ c2 (0)) ∼ 40 (T), caused a frenetic search for lightweight materials with similar crystalline structures and constituded by simple elements, and with potential to replace the already traditional Nb-Ti and Nb 3 Sn in the manufacturing of superconducting wires and tapes. However, despite the MgB 2 has high T c , the H c2 values decay rapidly when an external magnetic field is applied, mainly due to the poor pinning of the magnetic flux lines in the material. Furthermore, the plastic deformation process of the set containing the granular powder, constituded of metals used as diffusion barrier thermal and electric stabilizer, is a challenge, because the hardening of the metals by cold working and the accommodation of the superconducting powder. The objective of this work is to develop a process for the manufacture of multifilamentary MgB 2 wires, doped with carbon in the form of graphite and addition of diborides with crystalline structure similar to MgB 2 , as well as the optimization of the mechanical deformation processes, of the intermediate heat treatments and the characterization of the crystallographic, microstructural and superconducting properties of the wire. The methodology used for the production of the wire was the Powder-In-Tube (PIT) ex-situ with: milling of the powder in a high energy ball mill, chemical doping with graphite, addition of vanadium diboride (VB 2), magnesium in excess and use of stearic acid (C 18 H 36 O 2) as a process controlling agent. The mechanical deformation was done by means of rotary swaging. The final results suggest that the route used for the fabrication process of the graphite-doped MgB 2 multifilamentary wire with introduction of VB 2 , should be changed to use MgB 2 produced in laboratory from pure magnesium and boron, with a certificate of purity, using the in-situ methodology in a glove-box with controlled and monitored atmosphere with respect to the oxygen and humidity contents. The process described in this work improves methodologies shown in literature and guarantees the integrity of the wire during the entire fabrication process. In addition, it is suggested the use of an external reinforcing material, such as: iron, Glidcop (Cu-Al 15) or stainless steel (SUS 316L), so that the wire has a higher mechanical tensile strength and a lower cost.

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The effect of shape and deformation inex situMgB₂–W/Fe composite wires

Cited by 20 publications

References 15 publications

Improvement of current density by texture andI_canisotropy in thin filament MgB₂/Fe tapes

Improvement of current density by texture andI_canisotropy in thin filament MgB₂/Fe tapes

Critical current versus strain research at the University of Twente

Desenvolvimento da metodologia de fabricação de um fio supercondutor de MgB<sub>2</sub>

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The effect of shape and deformation inex situMgB2–W/Fe composite wires

Cited by 20 publications

References 15 publications

Improvement of current density by texture andIcanisotropy in thin filament MgB2/Fe tapes

Improvement of current density by texture andIcanisotropy in thin filament MgB2/Fe tapes

Critical current versus strain research at the University of Twente

Desenvolvimento da metodologia de fabricação de um fio supercondutor de MgB<sub>2</sub>

Contact Info

Product

Resources

About

The effect of shape and deformation inex situMgB₂–W/Fe composite wires

Improvement of current density by texture andI_canisotropy in thin filament MgB₂/Fe tapes

Improvement of current density by texture andI_canisotropy in thin filament MgB₂/Fe tapes