Grain structure and irreversibility line of a bronze route CuNb reinforced Nb3Sn multifilamentary wire (original) (raw)
Related papers
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.
J Mater Sci, 1987
Investigations were made of the superconducting transition temperature, To, the upper critical flux density, Be2, and the critical current density, Jc, of Nb3Sn layers in filamentary wire in a bronze matrix. The lattice parameter, a0, and Tc of Nb3Sn layers in 259-filament wire were determined after removal of the bronze matrix. The microstructure and layer thickness were studied using scanning electron microscopy. The diffusion formation of Nb3Sn phase at 1023 K was studied until the complete reaction of the niobium filaments. It was found that the Nb3Sn layer begins to form in the manufacturing process during the intermediate annealing at 793 K, and that there is a considerable degradation of critical parameters due to the nonstoichiometry of the Nb3Sn phase in layers thinner than 1 #m.
Cryogenics, 1985
Superconducting critical-current densities Jc in fields up to 24 T and at 4.2 and 1.8 K were measured for a number of commercial Nb3Sn wires which were alloyed with Ti. The best values of Jc (for the area excluding the stabilizing copper) at 20 T and at 4.2 and 1.8 K were 78 and 156 A mm-2, respectively. These values are approximately 10 and 4 times greater than values for the best 'pure' Nb3Sn wire for these measurement parameters. In order to achieve these high current densities at H>20 T, it was shown that nonuniformity of the filaments had to be minimized, It was also shown that the grain size of Nb3Sn is not very important in determining Jc at these high magnetic fields, and that achieving high values of critical magnetic field Hc2 is more important than small grain size.
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 (TC) 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 Nb3Sn compounds, and the Nb3Sn compound becomes more stable. Annealing processes were performed at temperatures ranging from 600°C to 900°C as well as various annealing time from 32 hours to 120 hours. The superconductivity of the samples were analyzed using resistivity measurement by cryogenic system under low temperature condition. The annealing can be performed optimally at the temperature of 600°C for 72 hours. However, the purity of the conductivity properties obtained at the optimal annealing temperature at 450˚C for 72 hours.
Microstructure development in Nb3Sn(Ti) internal tin superconducting wire
Journal of Materials Science, 2008
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.
Superconductor Science and Technology, 2014
The lattice parameter changes in three types of Nb 3 Sn superconducting wires during uniaxial stress-strain measurements at 4.2 K have been measured by high-energy synchrotron x-ray diffraction. The nearly-stress-free Nb 3 Sn lattice parameter has been determined using extracted filaments, and the elastic strain in the axial and transverse wire directions in the different wire phases has been calculated. The mechanical properties of the PIT and RRP wire are mainly determined by the properties of Nb 3 Sn and unreacted Nb. This is in contrast to the bronze route wire, where the matrix can carry substantial loads. In straight wires the axial Nb 3 Sn pre-strain is strongest in the bronze route wire, its value being smaller in the PIT and RRP wires. A strong reduction of the non-Cu elastic modulus of about 30% is observed during cool-down from ambient temperature to 4.2 K. The Nb 3 Sn Poisson ratio at 4.2 K measured in the untwisted bronze route wire is 0.35. The present study also shows that the process route has a strong influence on the Nb 3 Sn texture.
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...
Cryogenics, 1989
Binary and Ti + Mg alloyed NB3Sn wires both containing 19 x 132 and 55 x 588 filaments with diameters ranging between 1 and 5/~m have been produced by the internal Sn diffusion process, starting with cold hydrostatic extrusion. These wires exhibit a regular distribution of Sn cores and Nb filaments through the whole cross-section area. A heat treatment scheme including short preheating and a final reaction at 780°C yields Jc (non-Cu) values of 1.5 x 105 A cm-2 at 10 T for binary Nb3Sn wires. Ti + Mg alloyed Nb3Sn wires reacted according to the same scheme show higher Jc values above 12 T, i.e. 6.1 x 104 A cm-2 at 14 T, 1.8 ix 104 A cm-2 at 18 T. The present Paper includes measurements of Jc at applied fields up to 20 T and Jc as a function of the applied uniaxial strain, ~, at 13.5 T as well as T c after different heat treatments. The analysis was completed by the SEM determination of the A15 grain size with different additives and the measurement of the Sn concentration profiles by means of Auger spectroscopy for filaments located at different matrix regions. The absolute Sn concentration values were determined by EDX. It is found that the simultaneous addition of Ti and Mg to the Sn facilitates Nb3Sn grain growth and leads to finer grains.
IEEE Transactions on Appiled Superconductivity, 2001
In this work we present the properties of three multifilamentary (Nb,Ta)sSn wires, using a new Osprey processed bronze with 15.4wt.% tin content and ;Ub'l.Jwt.%Ta as core material. Wires were produced by hot hydrostatic extrusion and subsequent cold drawing with a few intermediate anneals. Two experimental wires with a wire length less than 100 m each were produced and the process parameters were successfully applied on an industrially manufactured wire with a total length of 8 km. Critical current density (Jc) measurements were performed up to 25 T at 4.2 K on all three wires heat treated by two different reaction anneals. High values of Jc (non copper, 10 FVm") and n were obtained for the conductor with a matridfilament ratio 3.0: Jc = 184 Amm" and n = 36 a t 18 T and 4.2 K, which are results comparable to nowadays commercially available wires. Microstructure analysis (i.e. the amount of reacted layer and the residual tin content of the bronze) tries to explain the differences in Jc values. Only small influences of the matrix/filament ratio and reaction parameters on the irreversibility field Bc2 (estimated by the Kramer extrapolation) and critical temperature Tc (measured by SQUID) have been observed.
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.