Multifilamentary Wires Research Articles

High Critical Current Density in the Textured Nanofiber Structure in Multifilament MgB2 Wires Made by the Powder-In-Tube (PIT) Technique.

We show that the structure of multifilament MgB2 wires made by the powder-in-tube (PIT) method can be texturized by annealing the structure under high isostatic pressure. Our results show that we obtained continuous fibers with a uniform diameter of 250 nm in all 36 filaments, a small grain size of approximately 50 nm and a high density of the superconducting material. These results contribute to a significant improvement in the critical current density in high magnetic fields, e.g., 100 A/mm2 at 14 T and 4.2 K.

Improving Bi-2212 multi-filament wire quality and superconductivity by cryogenic drawing

Bi2Sr2CaCu2O8+δ (Bi-2212)/Ag round wires were fabricated by cryogenic drawing under liquid nitrogen temperature (77 K). The influences of cryogenic drawing on the metallic sheath mechanical properties, filament densification, filament size uniformity, and superconducting properties have been systematically studied. Significant improvement of both strength and plasticity of Ag sheath was achieved under low temperature. Higher wire uniformity and densification state have been obtained by applying cryogenic drawing under 77 K, leading to the critical current density promotion by nearly 40 %. It is believed that cryogenic drawing of Bi-2212 wire is a feasible and effective way to improve the wire quality due to the mechanical reinforcement of metal sheath.

Optimum Filament Positions Within a MgB$_{2}$ Wire Resulting in Maximum Reduction of AC Losses

Transport current capability of MgB <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{2}$</tex-math></inline-formula> multifilamentary wires is intrinsically affected by the self and mutual magnetic inductance between superconducting filaments, which is a problem that depends on the geometrical distribution of the filaments. Any rise on this magnetic interaction can cause an increase in the AC losses of the system, which counteracts the efficiency of the wire and rises the cryogenics costs. Thus, in order to reduce the AC losses of multifilamentary MgB <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{2}$</tex-math></inline-formula> wires by finding an optimal arrangement of the MgB <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{2}$</tex-math></inline-formula> filaments, we present a comprehensive study for the optimal positioning of up to 7 and 13 filament wire configurations as common benchmarks. Varying the positions of the filaments within the copper matrix has shown a remarkable reduction in the AC losses of up to 60 <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><inline-formula><tex-math notation="LaTeX">$\%$</tex-math></inline-formula></b> the standard losses, a phenomenon which we have explained as a function of the calculated distributions of current density and magnetic field for the new wire designs. Likewise, a sudden rise in the AC losses of the multifilamentary wires with concentric arrangements of filaments has been found under certain configurations, where the magnetic saturation of the outer filaments can cause a notorious rise in the AC losses. This reveals how some multifilamentary designs can show enhanced energy loss characteristics whilst maintaining the same transport current conditions if a proper arrangement of the MgB <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{2}$</tex-math></inline-formula> wires is conceived prior to its manufacturing.

Present status of the high mechanical strengthened Nb3Sn superconducting wires for fusion applications

Nb3Sn superconducting wire will become the first candidate strand material for the high current capacity conductor on the magnet of a fusion prototype reactor (DEMO). Through the ITER procurement activities, however, the current sharing temperature (Tcs) and transport critical current (Ic) degradations by the Nb3Sn filament fracture due to the huge electromagnetic force was observed, and it was pointed out that the high mechanical strengthening of Nb3Sn superconducting wire is an important research issue for a future DEMO development. Therefore, we have been reconsidering on the Nb3Sn superconducting wire fabrication process in order to satisfy with the critical current density (Jc) and mechanical strength properties for DEMO design. In the past, various reinforcing materials such as the CuNb or oxide dispersed strengthening (ODS) Cu alloys have been added to Nb3Sn superconducting wires to increase their mechanical strength.In this paper, we reviewed the typical high mechanical strengthened Nb3Sn superconducting wires with various reinforcing materials and clarify the advantages and disadvantages of the high mechanical strength method using various reinforcing materials. In addition, we have proposed the “Internal Matrix Reinforcement” as the newly high mechanical strength method without the reinforcing material for Nb3Sn superconducting wires, which concept is clearly different from the conventional high mechanical strength method using reinforce material. The commercial-like internal matrix reinforced Nb3Sn superconducting multifilamentary wires were succeeded to fabricate and the present status of their superconducting properties and mechanical strength were discussed.

Maximum reduction of energy losses in multicore MgB2 wires by metastructured soft-ferromagnetic coatings

When compared with rare-earth coated conductors, magnesium diboride superconducting cables are known to show significant advantages by cost and easy production. However, the inherent difficulty for achieving a significant reduction of their magnetization losses in multifilamentary wires, without degrading the high critical current density that is so characteristic of the monowire, is considered as one of the major drawbacks for their practical use in high power density applications. Being this one of the major markets for superconducting cables, from fundamental principles and computational optimization techniques, in this paper we demonstrate how the embedding of the superconducting filaments into soft-ferromagnetic metastructures can render to their full magnetic decoupling, and therefore, to the maximum reduction of the energy losses that can be achieved without deteriorate the critical current density of the cable. The designed multifilamentary metastructure is made of NbTi coated MgB2 superconducting filaments in a Cu-matrix, serving as a reference for validating our model with actual experimental measurements in monowires and multifilamentary wires. The novelty in our computationally aided multifilamentary wires, is that each one of the filaments is embedded within a thin metastructure made of a soft-ferromagnetic layer and a resistive layer. We have found that for soft-ferromagnetic layers with magnetic permeabilities in the range of mu _{r}= 20–100, nearly a full magnetic decoupling between the superconducting filaments can be achieved, leading to efficiencies higher than 92%, and an overall reduction of the AC-losses (including eddy currents at the Cu-matrix) higher than 50%.

Investigation of transport mechanisms induced by filament-coupling bridges-network in Bi-2212 wires

One of the features unique in Bi-2212/Ag wires is the network of bridges between the filaments formed by grains grown through the Ag matrix during the partial-melt heat treatment process. Although these interconnections favor a redistribution of the current among the filaments allowing high critical current density, they represent a strong electrical coupling between the filaments themselves. Such a coupling increases the AC losses, present also in the case of the charge and discharge of DC magnets, and principal applications of this kind of superconductor. In this work, through transport and magnetic measurements and their comparison, we study the behavior of these bridges as a function of applied magnetic field and temperature and the implications they have on the electrical coupling. The experiment has been performed on two multifilamentary wires prepared by Groove-Die-Groove Powder In Tube process starting from two commercial Bi-2212 precursor powders: Nexans and Engi-Mat. The reported results show that the effective length scale on which the filaments are coupled is dependent on the field and temperature, passing from the filaments-bundle diameter at low field and temperature to single filament diameter at high field and temperature. Although the two samples have different Jc values, such filaments coupling behavior is common to both. We believe that these findings are very useful in magnet design.

Fundamental insight in the design of multifilament MgB2 joint for boosting the persistent-mode operation

Persistent-mode operation is a key feature of magnetic resonance image systems to improve the required field stability. The superconducting joint is known to be beneficial for reducing all the resistant components in an electrically closed-circuit. The joint technique of magnesium diboride (MgB2) multifilamentary wire, however, is the main obstacle to the use of magnet in practical applications. In response, herein, we designed and developed a unique configuration of superconducting joint to further enhance the interconnection of exposed cores between two 18-multifilamentary wires. It was confirmed that developed joint samples achieved high critical current similar to a non-jointed wire. The proposed joint technique was directly applied to the MgB2 single-turn coil and MgB2 magnet for estimating a joint property through persistent-mode operation. This work provides fundamental insights into the design of persistent-mode MgB2 magnets to boost magnetic resonance image systems.

Superconducting Joint Structures For Bi-2212 Wires Using a Powder-in-Tube Technique

Bi-2212/Ag superconducting wires are being considered as key conductor candidates for the development of high-field magnets. This work focuses on the design and testing of various joint structures for multifilamentary Bi-2212 wires using powder-in-tube techniques. The joints are made between the unreacted wires and subsequently heat treated with the wires. The microstructure and transport properties of different joint architectures including step joints, scarf joints and etched joints have been explored. The performance of etched-joints are found to be very sensitive to the etching parameters including etching time, making it difficult to develop a reliable jointing process. Scarf joints and step joints can carry higher currents (320 A and 475 A in self-field at 4 K) than the etched joints (225 A in self-field at 4 K) as a result of connecting a larger area of the exposed filaments without damaging the filaments.

Suppression of the critical current degradation under the compressive stress on the internal reinforcement bronze processed Nb3Sn wire using Cu-Sn-In ternary bronze alloy matrix

Typical large current capacity conductors for fusion magnet are often manufactured by the Cable-In-Conduit (CIC) method. The CIC conductor is fabricated by twisting multiple Nb3Sn strands and pure Cu wires, and huge local stress/strain concentration alike the point contact was observed in each twisted Nb3Sn strand applied to transverse compressive load based on the electromagnetic force. These concentrations caused to the Nb3Sn filament breakage and it was also a major factor of the current sharing temperature (Tcs) and critical current density (Jc) degradation on CIC conductor. Mechanical strength improvement of the Nb3Sn strand is required to realize superconducting magnet under higher electromagnetic force for a future DEMO. Recently, we succeeded to fabricate the internal matrix reinforcement bronze processed Nb3Sn multifilamentary wire using a Cu-Sn system ternary alloy matrix containing Indium (In) element.In this study, critical current (Ic) property with the in-situ compressive stress on the internal matrix reinforcement Nb3Sn wire was evaluated. The compressive stress obtained to the Ic deterioration of 5% on the internal matrix reinforcement Nb3Sn wire was confirmed at 150 MPa, and this stress was 3 times higher than Nb3Sn wire without reinforcement. We found that the internal matrix reinforcement was one of the great advantage methods to suppress the Ic degradation by the compressive stress.

Critical current density defined at low electric field criterion and energy margin of superconducting MgB2 wires in wide temperature and magnetic field range

High-temperature superconductors (HTS) and MgB2 may potentially improve the usability of superconducting magnets dramatically owing to their large energy margin. When HTS and MgB2 wires are used for magnets operated in the persistent current mode, such as in magnetic resonance imaging (MRI) scanners, the electric field generated in the wires must be lower than 10−10 V m−1. In this paper, critical current density, J c, defined at an electric field criterion of 10−10 V m−1 is evaluated from a magnetisation decay measurement for state-of-the-art monofilamentary MgB2 wires. By using the obtained J c, a critical line of our multifilamentary MgB2 wire is shown on the temperature-magnetic field plane. Here, the critical line is defined as a line on which an electric field of 10−10 V m−1 is generated at a coil current density of 150 A mm−2. The area inside the critical line is demonstrated to be large enough to fulfil the requirement of 1.5 T MRI scanners operated at 10K–15K. In addition, the iso energy-margin lines are shown on the temperature-magnetic field plane and compared with those of NbTi wires. The MgB2 wire has an order of magnitude greater energy margin than the NbTi wires in most of the area inside the critical line. This suggests that the MgB2 wire is highly unlikely to be quenched due to mechanical disturbances.

Evolution of precursor powders prepared by oxalate freeze drying towards high performance Bi-2212 wires

Bi2Sr2CaCu2Ox (Bi-2212) precursor powders were synthesized by the oxalate freeze drying (OFD) method. In comparison with the traditional method, the novel method could shorten the processing steps and thus improve the fabrication efficiency of precursor powder. The phase, microstructure and superconducting properties of Bi-2212 precursor powders and wires were characterized by X-ray diffraction, scanning electron microscopy and four-probe method, respectively. The thermal behavior, surface area and particle size of powders were also discussed. The results indicated that large surface area and small particle size might improve the reactivity and uniformity of powders. These properties were beneficial for the rapid and homogeneous formation of Bi-2212. High-purity crystallized Bi-2212 powders without Bi-2201 and alkaline-earth cuprates phases could be achieved. Furthermore, multi-filamentary Bi-2212 wires with OFD powders showed good microstructures without noticeable pores and large secondary particles. Therefore, high engineering critical current densities (Je) of 1619 A/mm2 and critical current densities (Jc) of 7039 A/mm2 were obtained in Bi-2212 wires at 4.2K, self field. It indicated that the oxalate freeze drying method would be a potential candidate for the mass production of high performance Bi-2212 wires.

Nausite and NbSn2 – Growth and distinction of structural related intermetallic phases in the Cu–Nb–Sn system

Processing of superconducting Nb3Sn multifilamentary wires requires several heat-treatment steps forming Nb3Sn at the final stage. During these heat treatments various intermetallic phases from the Cu–Nb–Sn system were intermediately formed, including a ternary phase, sometimes called “Nausite”. This phase derives from the binary NbSn2 phase by partial substitution of Nb by Cu (Martin et al., Intermetallics 80 (2017) 16-21). In this work, several samples containing NbSn2 and Nausite were investigated which show similar growth morphologies for both phases, also with some peculiarities, which are reflected by similarities of their atomic structures. Indeed, both phases belong to closely related crystal structures (CuMg2- and NiMg2-type) with comparable lattice parameters. This leads to similar EBSD Kikuchi patterns which causes difficulties in reliable phase distinction. In order to be able to use EBSD as a useful tool for local phase determination in the sub-μm range, phase distinction will be successful only when distinct minor, less prominent Kikuchi bands can be resolved and were used for indexing. This was revealed in this work using simulated Kikuchi patterns of both phases. Additionally, these bands overcome problems in orientation analysis of NbSn2 which arise from a pseudo-hexagonal symmetry.

Microstructural study on Sn–Zn/Cu–Ti diffusion reaction for internal tin Nb3Sn conductor development

To take advantage of Zn and Ti doping effects on improvement of diffusion behavior in the Sn–Cu mixing step and the Nb3Sn layer formation for the internal tin process, a diffusion couple configuration of Nb/Cu–Ti/Sn–Zn has been proposed. In this work, a fundamental study on the diffusion behavior of Sn–Zn/Cu–Ti, with different heat treatments, was conducted to aid in a better understanding of Nb3Sn phase formation, via internal tin diffusion. The first feature is that at 210∘C, the γ-CuZn phase forms at the reaction interface of Sn-20 wt%Zn and Cu, following which the β-CuZn and η-CuSn phases form at 400∘C. Compared with the Sn/Cu-12 wt%Zn system, Kirkendall voids appear to be suppressed, as few ε-CuSn phases, in which many voids grow, form in the Sn–Zn/Cu system. At 550∘C, a dendritic mixed phase of α-CuZn and δ-CuSn phases form. At this temperature, Sn appears to diffuse faster than in the case of the Sn/Cu–Zn system. It is observed that, after heat treatment at 550∘C, very fine compound particles of Sn–Ti are homogeneously distributed in the outer regions originally known to be the Cu–Ti sheath area. In the multifilamentary wires consisting of Nb/Cu–Ti/Sn–Zn diffusion couple configuration, no Ti rich compound layer was formed at the boundary of the Nb sub-elements, which overcomes the problem to suppress a smooth Sn and Ti diffusion into the Nb sub-element, when Ti is doped to Sn cores. Thus, no Ti-rich compound layer segregation, few void formations in the Sn–Cu mixing step and distributed fine Sn–Ti particles in the matrix accounts for the improved Jc characteristics in Nb/Cu–Ti/Sn–Zn wires. With regards to the mechanical properties, alloying of 20 wt% Zn to Sn cores increases the Vickers hardness of the Sn core to approximately 20kgf/mm2, almost double that of pure Sn or Sn-alloys with a small amount of Ti.

Dislocation and grain structure formation in Nb filaments of different geometry at fabrication of Nb3Sn-based superconducting wires

The structure of Nb filaments of different geometry artificially doped with NbTi alloy in Nb/Cu-Sn composites after various regimes of deformation beginning from the very first stages of fabrication of thin multifilamentary wires has been studied by transmission electron microscopy, optical microscopy and X-ray analysis. The structure of Nb filaments in composites of different designs is compared, and the development of dislocation and grain structure and texture of niobium in monolithic and assembled filaments under deformation with intermediate annealings is analyzed.

Electromechanical Properties Evaluation of Multifilamentary MgB2 Wires With Different Reinforcements

Magnesium diboride (MgB2) wires are highly attractive for various applications, given their high critical transition temperatures. The brittle compound filaments are protected by metallic sheaths that provide sufficiently strong reinforcement. The mechanical reinforcement provided to the brittle wires compensates for this weakness and enhances their electromechanical properties. Therefore, MgB2 wires can be considered a promising alternative to high-temperature superconducting wires in low magnetic fields such as those used in magnetic resonance imaging, wind power generators, and other applications. This study focused on the evaluation of the electromechanical behaviors of multifilamentary MgB2 wires of various configurations and with various sheaths. The irreversible strain/stress limits for I c degradation were evaluated under practical environmental conditions at a magnetic field of 2 T and a temperature of 20 K. The influences of the reinforcing materials on the electromechanical properties were investigated as was the temperature dependence of the mechanical properties.

Initial stages of Nb3Sn phase formation in Nb-bronze matrix composite wires investigated by means of electron microscopy

At present, Nb3Sn superconductors are becoming more popular in high magnetic fields. The growth law of Nb3Sn phase in a planar CuSn/Nb diffusion couple has been studied, whereas the formation mechanism of Nb3Sn phase in a cylindrical CuSn/Nb diffusion couple is still controversial. The purpose of this work is to investigate the growth exponent of Nb3Sn phase at the initial stage of annealing by use of scanning electron microscopy (SEM) through which the thickness of Nb3Sn layer can be obtained. In this study, bronze-processed Nb3Sn multifilamentary wires with different annealing time were investigated. The Nb3Sn phase was formed during isothermal annealing at 670 °C by solid-state diffusion, which was accomplished by the movement of Sn atoms from the CuSn/Nb3Sn interface to Nb3Sn/Nb interface. However, the formation mechanism of Nb3Sn phase at the initial stage of annealing is still not well understood. Microstructural evolution of Nb3Sn phase during isothermal annealing was studied by SEM. The mean thickness of the Nb3Sn layer ( $$\Delta x_{{{\text{Nb}}_{ 3} {\text{Sn}}}}$$ ) is expressed as a power function of the annealing time (t) by the equation $$\Delta x_{{{\text{Nb}}_{ 3} {\text{Sn}}}}^{2} = k(t/t_{0} )^{n}$$ , where t0 is the unit time, k is the reaction rate constant and n is the growth exponent. The growth exponent has the average value of 0.82, which means that the formation of the Nb3Sn phase is both governed by the interface reaction and the grain boundary diffusion.

Scanning Hall-probe microscopy for site-specific observation of microstructure in superconducting wires and tapes for the clarification of their performance bottlenecks

This paper reports a diagnostic method for clarifying performance bottlenecks in superconducting wires and tapes for their further performance enhancements. In particular, our achievements by scanning Hall-probe microscopy (SHPM), which worked well for selecting positions for microstructure observation by SEM, TEM, and x-ray CT, are introduced. This hybrid microscopy offers the information of the direct relationship between the performance of a practical-scale superconducting wire or tape and its origin in micro-scale or nano-scale structure. As such examples, characterization results for an MgB2 multi-filamentary wire, a commercially available long RE-123 coated conductor, and a striated multi-filamentary coated conductor are reported in this paper through reviewing our past studies.

Role of the Complex Interface Between Bi2Sr2CaCu2Ox Filaments and the Ag Matrix in the Mechanical and Electrical Behaviors of Composite Round Wires

For a superconducting Bi <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Sr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> CaCu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> (Bi2212) multifilamentary composite round wire (RW), typically the interface between Bi2212 filaments and the Ag matrix become extremely complex after heat treatment, and all the time the question of how the unique interface structure affect the macro properties such as mechanical, electrical, and thermal behaviors has not been satisfactorily answered, mainly because it is very hard to <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> measure the microstructure evolution and further evaluate its effect on these macro properties. Therefore, for this purpose, in this article, we made the modeling and numerical study on the role of the Bi2212/Ag interface in the mechanical and electrical behaviors of composite RWs. By using the randomly generated polygons method, we first reconstructed the cross section of Bi2212 composite RWs, especially in this reconstruction the complex Bi2212/Ag interface can be effectively characterized. On both of two models with and without the complex interface, we obtained the thermally residual stresses and strains due to cooling down from heat treatment, and then the mechanical response from the applied tensile strain. The comparative study further revealed that, for a practical Bi2212 RW with the complex interface, the distributions of the stress and strain are more uniform, which make the wire tend to safely and equivalently increase its limiting load capacity according to the maximum principal stress theory. In order to deeply understand the degradation of the critical current <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_c</i> under applied tensile strain <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\varepsilon $</tex-math></inline-formula> of Bi2212 RWs, we presented a current sharing model in which the current shares both in Bi2212 filaments and surrounding Ag matrix, taking into account the obstacle of cracks in the filament. By comparing the calculated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${I_c} - \varepsilon $</tex-math></inline-formula> curve with experimental data, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_c</i> degradation with the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\varepsilon $</tex-math></inline-formula> was very well interpreted by the mechanical damage and fracture of the microstructure of Bi2212 RWs.

Role of Cr-coating by electroplating method on fabrication and transport properties of Fe/Cr/MgB2 wires

This study has focused on the use of chromium metal as a chemical barrier in the production of in situ MgB2 wires. The chromium metal was plated homogeneously into the initial iron tube by electroplating in order to produce in situ mono-core and multi-filamentary Fe/Cr/MgB2 wires. Cr metal has maintained its continuity through the wire drawing, but inhomogeneous thickness of Cr-coating at the Cr/Fe interface region without chemical reaction to each other is revealed. The in situ mono-core Fe/Cr/MgB2 wire with a diameter of 1.32 mm and multi-filamentary wires with 1.00 mm and 1.26 mm diameters were produced by PIT process and heat treated at different annealing temperatures and times. Transport and structural investigations of the wires indicated locally positive effect of Cr-coating on Fe2B phase formation, transport properties, and the core structure of MgB2 wires. The mono-core Fe/Cr/MgB2 wire-coded A24 has the highest engineering critical current density of 56 A/cm2 at 30 K under 6.5 T.

Mechanical Strength Evaluation of the Internal Matrix Reinforced Nb3Sn Multifilamentary Wires Using Cu–Sn–In Ternary Alloy Matrix

We investigated the simple internal reinforcement method using special reinforcement ternary bronze alloy matrix on the bronze processed Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wire. The Cu-Sn-Zn ternary alloy matrix was transformed to the (Cu, Zn) solid solution after Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn synthesis based on the solid solution strengthening mechanism. For the further mechanical strength improvement, we focused on the Indium (In) as the more effective solute element for the “internal matrix strengthening”, and succeeded to fabricate the bronze processed Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn multifilamentary wire using various Cu-Sn-In-(Ti) ternary alloy matrices. Changes of the Vickers hardness before and after Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn synthesis and the transport critical current (Ic) under the uniaxial tensile deformation were evaluated. Vickers hardness of the matrix after Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn synthesis on the Cu-Sn-In ternary alloy matrix samples was higher compared with the conventional bronze and the Cu-Sn-Zn ternary matrix samples. On the other hand, the tensile stress obtained to the maximum peak Ic value on the Cu-Sn-In ternary alloy matrix sample was estimated to approximately 265 MPa, and this value was much higher than those of the Cu-Sn-Zn ternary matrix and conventional bronze processed samples. We found that the In element would become more attractive solute element than Zn element for the internal reinforcement ternary matrix.