On the correlation of microstructure and electromagnetic properties of heavily cold worked Cu20 wt% Nb wires (original) (raw)
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Correlation of superconductivity and microstructure in an in-situ formed Cu20%Nb composite
Physica Status Solidi (a), 1994
The normal and superconducting properties of a wire-drawn Cu–20%Nb alloy, forming a fibre reinforced in-situ composite, are investigated. The results are correlated to microstructural attributes of the composite and compared to findings in analogously processed pure Cu. The microstructure of Cu–20%Nb is characterized by the curled and elongated morphology of the superconducting Nb ribbons which are embedded in the Cu matrix. Whereas superconductivity in the heavily deformed composite is accomplished by the Nb filaments, the normal conducting properties which are determined by the Cu phase are considerably influenced by the Nb filament spacings. Only a slight dependence of superconductivity on the enhancement of the density of internal boundaries due to different degrees of deformation was observed.Die normal- und supraleitenden Eigenschaften einer drahtgezogenen Cu–20%Nb-Legierung, die sich zu einem faserverstärkten Verbundwerkstoff ausformt, werden untersucht. Die Ergebnisse werden mit den mikrostrukturellen Merkmalen des Verbundwerkstoffes korreliert und mit Resultaten von entsprechend verformtem reinem Cu verglichen. Die Mikrostruktur in Cu–20%Nb wird durch die gekrümmten und langausgezogenen Nb-Filamente, die in der Cu-Matrix eingebettet sind, charakterisiert. Während die Supraleitung in dem hochverformten Verbundwerkstoff über die Nb-Filamente entsteht, werden die normalleitenden Eigenschaften, die durch die Cu-Phase bestimmt werden, nachhaltig von den Nb-Faserabständen beeinflußt. Bei den unterschiedlich verformten Proben wird eine nur geringe Abhängigkeit der supraleitenden Eigenschaften von der Dichte der inneren Grenzflächen beobachtet.
Z. Metallkde. 86 (1995) 6
Fiber or ribbon reinforced in situ metal matrix composites (MMCs) consisting ofCu and 20 mass% Nb were produced by large strain wire drawing and cold rolling of a cast ingot. The microstructure of the composites was studied by use of scanning and transmission electron microscopy. The normal and superconducting properties of the wires and sheets in the presence of externally imposed magnetic fields were investigated and compared with the electromagnetic properties of pure Cu and Nb. The observations are discussed in terms of the microstructural changes during wire drawing and rolling. The current results substantiate that the . amount of internal phase boundaries and the filament spacing have considerable influence on the normal and superconducting properties of Cu-20 mass% Nb. On the basis of the current findings potential industrial applications are discussed .
Measurement of filament spacing in deformation processed CuNb alloys
Acta Metallurgica et Materialia, 1991
Al~ract-Previous studies of Cu-20 vol.% Nb alloys used optical and SEM techniques to evaluate the thickness and spacing of the Nb filaments. It had been known that the filament sizes were smaller than the resolution limit of the SEM at high deformation strain but it was assumed that this problem would not significantly change the observed trends. Results of this TEM study using dark-field techniques on the same materials show that the previous SEM measurements significantly overestimated the spacing at the higher deformations. Analysis of resistivity data on the samples also confirms this result. The strength dependence on Cu channel spacing, tcu, was found to display a large transition region, with the dependence changing from a t? ° 5 at low strains to a t~ °38 at high strains. The significance of these results is discussed. It is also pointed out that the filament sizes observed at high strains in these materials range to below 20 nm and they exhibit strength/filament size characteristics similar to vapor deposited nanocrystalline materials. R~mma~-Des &udes ant&ieures d'alliages Cu-20%Nb en volume ont utilis~ des techniques optiques et la MEB pour 6valuer r6paisseur et l'espacement des filaments de Nb. On a montr6 que les tailles des filaments 6taient plus petites que la r6solution limite du MEB fi des d6formations 61ev&s, mais on a suppos~ que ca probl6me ne changeait pas beaucoup les tendances observ~es. I_as r~sultats de cette 6tude par MET qui utilise les techniques de champ sombre sur les m6mes mat6riaux montre que les mesures ant6rieures par MEB ont surestim6 consid6rablement respacement aux plus fortes d6formations. L'analyse des donn6es de r&istivit6 sur ces &hantillons confirme aussi ca r&ultat. La d6pendanca de la r6sistance m&anique vis fi vis de I'espacament des canaux de Cu, tcu, r~v61e une large r6gion de transition, la loi de variation passant de t6 °'s aux faibles d6formations ~i t6 °.3s aux fortes d6formations. La signification de cas r~sutats est discut~e. On montre aussi, que les taffies de filaments observ&s aux fortes d6formations dans ces mat&iaux peuvent descendre fi moins de 20 nm et qu'elles montrent des caract6ristiques r6sistance mL'canique/taille des filaments semblables aux mat&iaux nanocristallis~s d6pos~s en phase vapeur. ZmmnmenfmJ.mng-Friihere Untersuchungen der Legierung Cu-20 Vol.-% Nb wurden mittels optischer und rasterelektronenmikroskopischer Methoden durchgeffihrt, um Dicke und Abstand der Nb-Fasern zu bestimmen. Es ist bekannt, dab die Fasergr6~ bei hoher Verformung kleiner ist als die Aufl6sung des SEM, es wurde aber angenommen, dab diese Frage die beobachteten Trends nicht deutlich beeinflussen k6nne. Ergebnisse der vorliegenden elektronenmikroskopischen Untersuchung, erhalten mit Dunkelfeldabbildung, zeigen, dab die frfiheren SEM-Ergebnisse den Abstand bei h6herer Verformung deutlish fiberseh/itzten. Widerstandsmessungen best~itigen dieses Ergebnis. Die Abhfingigkeit der Festigkeit yon dem Abstand tcuder Cu-Kan~.le weist einen grogen 1Dbergangsbereich auf, in dem die Abh~ingigkeit yon t6 °'5 bei niedriger Dehnung auf t6 °'~ bei hoher Dehnung steigt. Die Bedeutung dieser Ergebnisse wird diskutiert. AuBerdem wird darauf hingewiesen, dab die bei hoher Dehnung beobachtete Fasergr61]en bis unterhalb 20 nm liegen und Festigkeits/Fasergr6~n-Charakteristika aufweisen fihnlich den aus der Dampfphase abgeschiedenen nanokristallinen Materialien.
IEEE Transactions on Applied Superconductivity, 2000
In this work we focus on the microstructural and magnetic characterization of CuNb/Nb 3 Sn wires with different architectures (design and reinforcement). The microstructural characterization was performed using scanning electron microscopy. AC magnetic susceptibility was measured with field applied both parallel and perpendicular to the wire axis. The heat treatment performed to form the A-15 superconducting phase leads to partial spheroidization followed by coarsening of the Nb filaments in the reinforcement material. The differences concerning the microstructure of the reinforcement material among the investigated wires were reflected in the broadening of the superconducting transition of Nb, more evident for a field applied parallel to the wire axis. From the magnetic data the wires were also compared in terms of the superconducting volume fraction.
Jurnal Sains Materi Indonesia EFFECT OF ANNEALING ON Cu-Nb-Sn SUPERCONDUCTING WIRE
2015
EFFECT OF ANNEALING ON Cu-Nb-Sn SUPERCONDUCTING WIRE. The most common application of superconductors is done in the form of superconducting wire. Among the existing types of superconductors, Cu-Nb-Sn superconductors are the most widely used as a wire, producing a high magnetic field. But the critical temperature (T C) values of its superconductors are low enough so that the resulting magnetic field and its application fields are limited. In this study we investigated the effect of annealing treatment on the Cu-Nb-Sn superconducting wire. Note that the process of annealing on superconducting wire can increase the value of the critical temperature of 8K to 16K. The increase is predicted because of the forming of Nb 3 Sn compounds, and the Nb 3 Sn compound becomes more stable. Annealing processes were performed at temperatures ranging from 873K to 1173K as well as various annealing time from 32 hours to 120 hours. The superconductivity of the samples were analyzed using resistivity mea...
phys. stat. sol. (a) 147, 515 (1995)
A fibre reinforced in situ metal matrix composite (MMC) consisting of Cu and 20massY0 Nb is manufactured by large strain cold rolling. The microstructure of the composite is investigated by means of optical and electron microscopy. The normal conducting properties of the MMC sheets in the presence of external magnetic fields are studied and compared to the electromagnetic behaviour of pure Cu and Nb sheets. The findings are discussed in terms of the microstructural changes which take place during rolling deformation. The resistivity of the MMC is simulated by assuming inelastic scattering of the condution electrons at the internal phase boundaries. Both, experiment and simulation, substantiate that the amount of internal boundaries and the filament spacing have considerable influence on the normal conducting properties of Cu-20 mass% Nb.
Supercond. Sci. Technol. 19 (2006) 1233–1239
We report on the influence of the microstructure on the AC and DC magnetic properties of Cu–3.5% Nb nanofilamentary wires. Samples obtained from a single Cu–3.5% Nb wire were subsequently submitted to different plastic strain levels via drawing so that their microstructure was altered. Noticeable differences are observed in their isothermal DC magnetization curves that present a double-peak structure. The first peak, which occurs at low magnetic fields, is attributed to superconductivity induced in the Cu matrix due to the proximity effect. It is argued that the second peak is related exclusively to niobium. The dependence of these two distinct peaks on the characteristic nanometre length scales of the samples, i.e. dimension of the Nb filaments and interfilamentary spacing, are discussed.
Microstructural characterization of high strength high conductivity Cu-Nb microcomposite wires
Purpose: The properties and the microstructure of cold drown Cu-Nb composites have been investigated for their potential use as conductors in high field magnets. Nowadays, there is much activity in the development of such conductors all over the world. Design/methodology/approach: This study was aimed to investigate microstructure, mechanical and electrical properties of Cu-Nb15 wires. The investigated materials have been processed by vacuum furnace melting and casting, further hot forging and cold drawing. Alternatively material has been processed by one of the SPD (severe plastic deformation) method using oscillatory turning die pressing. Microstructure has been observed by optical and electron microscopy technics. Findings: The ultimate tensile strength versus cold deformation degree have been presented. These changes have been discussed in relation to the microstructure evolution. Practical implications: The obtained mechanical and electrical properties (UTS over 900 MPa and ele...
Mechanical and superconducting properties of 6-filament MgB2 wires reinforced by Cu, Cu–Nb and NbTi
Physica C: Superconductivity, 2012
The mechanical and superconducting properties of MgB 2 wires heat treated at various conditions have been investigated. Superconducting MgB 2 wires, fabricated by the powder-in-tube (PIT) method, show a transition temperature T c at 32.4 K for the as-rolled wire as shown by dc-resistivity measurement. It is found that the T c is improved (37.3-38.4 K) by subsequent Ar annealing treatment under various sintering temperatures and times. Remarkably, the annealed samples show significant improvement in the overall quality of the samples. On annealing at 1323 K for 0.6 ks, we obtained the best quality sample with a J c of 470 A mm −2 at 2.0 T. In order to find out the irreversible field (B irr ), the technique of the Kramer plot was applied. The B irr obtained was 7.6 and 9.6 T, for the as-rolled as well as the annealed samples at 1073 K for 3.6 ks, respectively. The mechanical properties were measured under tensile load. The yield stress was 450 MPa for the as-rolled sample and decreased by annealing at 1323 K for 0.6 ks to 110 MPa. After the wires were heat treated at temperatures between 1073 and 1323 K and tensile-stressed up to their yield stress at room temperature. The critical current measurements were carried on such samples at 4.2 K under applied magnetic fields of 2 and 5 T. The stress level for the 95% tolerance of critical current was determined to 97 MPa.