Composite MgB2 wires were made by using the powder-in-tube method and commercial MgB2 powder in Fe and stainless steel sheaths. Various deformation processes were used. Two-axis rolling produced the highest powder density, leading to the best JC (0T, 4.2K) of 55000A/cm2 in as-deformed wire. Therefore, 4-core wire had also been made by 2-axis rolling. The short samples were subjected to annealing (850 to 1100C, 0.5h) in Ar, which led to apparently improved JC values, 25000A/cm2 at 4T and around 106A/cm2 in the self-field (at 4.2K). An interdiffusion layer between MgB2 and the Fe or SS sheath was observed and analyzed. The stainless steel sheath reacted more intensely than did Fe, due to the presence of Ni and Cr elements. Transport currents were measured at 4.2 to 25K and an external magnetic field of 0 to 8T. An engineering current density level of 104A/cm2 was used to estimate the magnetic field possibly generated by coils wound from MgB2 composite wires.

Properties of As-Deformed and Post-Annealed MgB2/Fe(Fe-Alloy) Composite Wires. P.Kovác, I.Hušek, C.Grovenor, C.Salter: Superconductor Science and Technology, 2003, 16, 292-6