Processing Parameters that Affect the Tolerable Bending Diameter of Reacted MgB₂ Wires

In this study, tolerable bending diameters of reacted MgB₂ wires fabricated to produce varying outer sheath materials, numbers of MgB₂ filaments, and sheath layer thickness were investigated. The result showed that the tolerable bending diameters of the MgB₂ wires with Cu, Cu–Ni, and Monel sheaths were the same. This implies that the sheath material strength of these wires does not affect the tolerable bending diameter. In addition, mono-filament wires were more vulnerable to bending strain than multi-filament wires due to their porous microstructure. An increase in the sheath layer thickness of the MgB₂ wires resulted in less degradation of the wires at high bending strains because the strain acting on the MgB₂ filaments was reduced by the thick sheath layer. This study generally confirmed that the sheath layer thickness of the MgB₂ wire is a key factor to increase the bending tolerance of the wire.