Properties of seven-filament in situMgB2/Fe composite deformed by hydrostatic extrusion, drawing and rolling

Abstract

Seven-filament MgB2/Fe wires and tapes were made by in situ processing using hydrostatic extrusion, rolling and drawing.Microhardness measurements have shown that the density of as-deformed cores reflects theapplied deformation and follows the iron sheath hardness. The filament size was reduced from245 µm downto 19 µm by rolling and the critical current densities of samples with different coresizes and deformation routes were compared. The highest current density wasmeasured for the tape deformed by two-axial rolling and a filament size of60 µm. Thinner filamentsshow lower Jc values due to hard inclusions present in low-purity boron powder (boron oxide), whichreduce the transport current substantially. The obtained results show that a propercombination of extrusion and rolling deformations leads to high filament density in wiresand tapes, which results in high transport current density.