Effect on the phase formation of Bi-2223 in some Ag-alloy sheathed PIT tapes

Zeng, Rong; Guo, Yuan; Tanaka, Yoshiaki; Horvat, J.; Ionescu, Mihail; Beales, T.P.; Appley, M; Liu, H.K; Dou, Shi Xue

doi:10.1016/s0921-4534(98)00503-6

Cited by 23 publications

(14 citation statements)

References 12 publications

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“…This means that the conversion of Bi2223 phase was almost completed in the Ag-Mg alloy sheath tapes. As shown in figure 4(a), there are few peaks of the Bi2223 phase after the first sintering although the peak intensities for Bi2223 were comparable to those for Bi2212 for the pure Ag sheathed tapes after the first sintering as reported in [14]. The observed results shown in figures 3 and 4 suggest that the reaction rate for forming Bi2223 in the Ag-Mg sheathed tape was slower than that for pure Ag tape while the conversion reaction was completed after the final sintering.…”

Section: Standard Patternsupporting

confidence: 71%

“…In addition, the use of a hard alloy sheath instead of soft pure Ag could suppress the sausaging effect by matching the hardness between the sheath and the filament cores [1]. Many Ag alloy sheath materials such as Ag-Cu [2][3][4][5][6][7][8], Ag-Mg [9][10][11][12][13][14] and Ag-Al [6] have been examined for achieving high mechanical strength. However, when the Ag alloys are used for sheath material directly contacting superconducting filaments, the superconducting properties of the tapes have been degraded in many cases.…”

Section: Introductionmentioning

confidence: 99%

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The effect of rolling and sintering steps on microstructure andJ_cproperties of Bi2223 wire sheathed with Ag–Mg alloy

Nakamura

Saigo²,

Torii³

et al. 2006

Supercond. Sci. Technol.

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The use of an Ag alloy sheath is effective for improving the mechanical strength of Bi2223 wires although it may easily decrease J c through undesired reactions with Bi2223 superconductor. In this study, Bi2223 tapes sheathed with Ag-Mg alloy, which is less reactive with the superconducting phase, were fabricated, and the effect of processing on the microstructure and J c properties was investigated. The Ag-Mg alloy sheathed Bi2223 tapes showed many Bi2223 crystal outgrowths when they were fabricated with the same pattern as was used for fabricating pure Ag sheathed tape, and the J c value of the tapes became poorer: about 9 × 10 3 A cm −2 . This degradation of J c is attributed to the poorer crystal alignment seen as many outgrowths, which would be caused by the reduction of the conversion rate of Bi2223. To improve the crystal alignment and J c values, the rolling and sintering patterns were improved. It was found that the addition of intermediate rolling and careful selection of the sintering time could be used to suppress the formation of outgrowths effectively and improve the J c value to 1.4 × 10 4 A cm −2 through the improvement of the crystal alignment. This means that the timing of the rolling step(s) should be selected at effective point(s) in the phase development of Bi2223 crystal.

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Section: Standard Patternsupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

The effect of rolling and sintering steps on microstructure andJ_cproperties of Bi2223 wire sheathed with Ag–Mg alloy

Nakamura

Saigo²,

Torii³

et al. 2006

Supercond. Sci. Technol.

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“…Hardening of Ag alloys is predominately accomplished by internally oxidizing solute species such as Mg [12][13][14]16], Ni [17,18], Cu, Ti [14,19], Pr [20,21], Mn [14], etc, which provide solid solution strengthening [22]. During internal oxidation, the alloying element oxidizes, forming oxide precipitates.…”

Section: Introductionmentioning

confidence: 99%

High strength oxide dispersion strengthened silver aluminum alloys optimized for Bi₂Sr₂CaCu₂O_8+xround wire

Kajbafvala¹,

Nachtrab²,

Kumar³

et al. 2013

Supercond. Sci. Technol.

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High strength dispersion strengthened (DS) Ag/Al alloys with various Al content are studied as candidates for sheathing Bi 2 Sr 2 CaCu 2 O 8+x (Bi2212) wire. The Ag/Al alloys are fabricated by powder metallurgy and internally oxidized in pure oxygen. The time and temperature of the internal oxidation heat treatment is varied to maximize the strength after undergoing the Bi2212 partial melt process (PMP). Vickers micro-hardness number (HVN), room temperature tensile behavior, optical and scanning electron microscopy, ion channeling contrast imaging using a focused ion beam and electrical resistivity measurements are used to characterize the alloys. An Ag/0.2wt%Mg (Ag/Mg) alloy is used for comparison. Results show that internal oxidation at 650-700 • C for 4 h produces the highest HVN for the DS Ag/Al alloy; when oxidized at 675 • C for 4 h the HVN, yield strength and tensile strength of the DS Ag/Al are 50% higher than the corresponding values of Ag/Mg. Microstructural observations show that Al 2 O 3 precipitates play the main role in strengthening the DS Ag/Al alloy. The alloy retains its fine grain structure and strength after PMP heat treatment.

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“…(3g), it can be seen that Bi2223 phase (grey) is present in a large amount (95%), while there are very small amount (3%) of Bi2212 (thin white layer) and Bi3221 (2%). This is because Bi2201 was converted into superconducting phase during sintering at lower temperature (810 -825 ) [11], and slow cooling eliminated Bi3221 [12].…”

Section: B Interface Between Core and Sheathmentioning

confidence: 99%

Microstructure Observations of Ag and Ag-Alloy Sheathed Bi2223 Tapes

Liu

Zeng

2007

IEEE Trans. Appl. Supercond.

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Abstract-37 filament Bi2223 tapes with different configurations of Ag, AgAu7wt% AgSb0.6wt% and AgMg0.2wt% as the precursor and restack sheaths were fabricated using commercial Bi2223 precursor material and powder-in-tube techniques. Short length samples were heat treated at a temperature in the range of 832 C to 846 C for the first stage (HT 1), followed by a second stage (HT 2) at 825 C for 40 h and slow cooled to 785 C. An intermediate roll pass was performed between the heat treatment stages. The critical current (I c ) of the tapes was measured at 77 K in self-field and in fields up to 1 T. The microstructure of the alloy sheaths was examined using optical microscopy, and the Bi2223 filaments after HT 1 and HT 2 were examined using scanning electron microscopy (SEM). It was observed that the sequence of hardness, tensile strength, and critical bend strains from higher to lower levels is very much related to the grain sizes in the restack sheath. J c of the tapes in zero field and in applied field was influenced by the phase composition, core density, grain connectivity, grain alignment and the interface between the Bi2223 filament and sheath.

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Effect on the phase formation of Bi-2223 in some Ag-alloy sheathed PIT tapes

Cited by 23 publications

References 12 publications

The effect of rolling and sintering steps on microstructure andJ_cproperties of Bi2223 wire sheathed with Ag–Mg alloy

The effect of rolling and sintering steps on microstructure andJ_cproperties of Bi2223 wire sheathed with Ag–Mg alloy

High strength oxide dispersion strengthened silver aluminum alloys optimized for Bi₂Sr₂CaCu₂O_8+xround wire

Microstructure Observations of Ag and Ag-Alloy Sheathed Bi2223 Tapes

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Effect on the phase formation of Bi-2223 in some Ag-alloy sheathed PIT tapes

Cited by 23 publications

References 12 publications

The effect of rolling and sintering steps on microstructure andJcproperties of Bi2223 wire sheathed with Ag–Mg alloy

The effect of rolling and sintering steps on microstructure andJcproperties of Bi2223 wire sheathed with Ag–Mg alloy

High strength oxide dispersion strengthened silver aluminum alloys optimized for Bi2Sr2CaCu2O8+xround wire

Microstructure Observations of Ag and Ag-Alloy Sheathed Bi2223 Tapes

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The effect of rolling and sintering steps on microstructure andJ_cproperties of Bi2223 wire sheathed with Ag–Mg alloy

The effect of rolling and sintering steps on microstructure andJ_cproperties of Bi2223 wire sheathed with Ag–Mg alloy

High strength oxide dispersion strengthened silver aluminum alloys optimized for Bi₂Sr₂CaCu₂O_8+xround wire