Single- and 4-core MgB2 wires were made via the powder-in-tube method, using commercial MgB2 powder and 2-axis rolling deformation in an Fe sheath. The deformed wires were subjected to annealing (950C to 1100C, 0.5h) in Ar. The interface layer thickness of 10 to 25.4μm, caused by interdiffusion and reaction between the MgB2 core and the Fe sheath, was observed in all of the annealed wires. The transport currents of as-deformed and post-annealed wires were measured at 4.2K in external magnetic fields of 0 to 5.5T. The presence of a ferromagnetic sheath in MgB2 composite wire influenced the JC(B) characteristics; leading to JC hysteresis and JC anisotropy, which was more pronounced for those that had not been annealed (weakly linked grains) in comparison to well-connected MgB2 grains after recrystallization.

Transport Currents of Two-Axially Rolled and Post-Annealed MgB2/Fe Wires at 4.2K. P.Kovác, I.Hušek, T.Melišek: Superconductor Science and Technology, 2002, 15, 1340-4