The addition of W particles had led to an improvement of the current-carrying capacity of ex situ MgB2 wires, due to an improved internal stability. The best performance had been observed for 5 to 10wt% of W additions and therefore this content was used here for multi-core wires made by using the rectangular wire-in-tube technique. Transport current measurements showed how the variable wire shape (rectangular, circular or tape) as well as additional mechanical deformations (twisting, bending and axial stresses) influenced the critical current density of 4-filament MgB2–W/Fe wires in external magnetic fields ranging up to 11T. Critical current degradation by twisting, bending at room temperature and axial stresses at 4.2K were considered. It was found that the addition of W particles had no effect upon the value of the irreversible strain limit

The Effect of Shape and Deformation in ex situ MgB2–W/Fe Composite Wires. P.Kovác, I.Husek, T.Melisek, M.Dhallé, M.Müller, A.Den Ouden: Superconductor Science and Technology, 2005, 18, 615-22