The influence of the roll diameter in flat rolling of of superconducting in situ and ex situ MgB2 tape

Michael Halloway Hancock, Niels Bay

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    Applying the powder in tube (PIT) method, single-filament MgB2/Fe wire and tape has been manufactured applying both the ex situ and the in situ approach. The influence of the roll diameter in three-step flat rolling on the powder density and critical temperature has been examined using rolls of 70, 150 and 210 mm in each step. The investigation has shown that the in situ powder is more readily compacted than the ex situ powder, with an average increase of relative density after mechanical processing of 37% for in situ powder and 19% for ex situ powder. Statistical analysis showed that the choice of roll diameter had the largest influence in the first of the three reductions used in the flat rolling. In this first reduction, for ex situ tapes, rolls of 70 or 150 mm proved best, whereas the 70 mm roll appeared best for in situ tapes. Overall, the evidence suggested that the combination of the 70 mm roll in the first and second reductions followed by the 150 mm or 210 mm roll in the last reduction was the optimum strategy for both powder types. AC susceptibility testing showed that for the in situ tapes there was no correlation between the powder density and the critical temperature. For ex situ tapes the critical temperature correlated to some degree with the powder density; also the critical temperature proved to be more sensitive to the powder density for ex situ samples.
    Original languageEnglish
    JournalSuperconductor Science and Technology
    Volume20
    Pages (from-to)886-890
    ISSN0953-2048
    Publication statusPublished - 2007

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