Effect on Deformation Process of Adding a Copper Core to Multifilament MgB2 Superconducting Wire

Using the PIT method, multifilament wire with different packing strategies has been manufactured. In all, three types of wire have been investigated, a 19-filament configuration using ex-situ powder in an Fe-matrix and two 8-filament configurations in an Fe-matrix applying a copper core, one using in-situ and another using ex-situ powder. The effect on the annealing requirements during mechanical processing of adding such a copper core has been investigated. The results show that the number of required annealings drops by about a factor of one half with the addition of a copper core. This finding is supported by numerical simulations of the deformation process which indicate that tensile stresses are concentrated around the middle of the wire during the drawing process. As such, strategic packing of the multifilament configuration can reduce the need for annealing during the mechanical deformation process. It is also found that the multifilament configuration using in-situ powder requires less annealing than the ex-situ counterpart. This is most likely due to the fact that in-situ powder is more readily compacted than ex-situ powder.