Superconducting and microstructural properties of (Mg+2B)+MgB2/Cu wires obtained by high gas pressure technology

In order to improve the overall critical current characteristics of Cu sheathed in situ MgB2 wires a special architecture of the wire, and processing parameters were used. The study presents the influence of the ex situ MgB2 chemical barrier between ex situ core and Cu, suppressing the reaction of Cu with Mg. Wires, doped with 10 at.% SiC of 18 nm average grain size, were fabricated from MgH2 and B or from Mg and B powders, using the powder-in-tube method. The methods of rotary swaging or drawing were used as the alternating wire-forming processes. The samples were annealed under high Ar gas pressure (hot isostatic pressing) at 750 degrees C and 1.0 GPa for 15 and 30 min. A significant difference in Cu distribution across the wires for a long and short time of sintering was observed. The formation of microstructure in the powder-in-tube process and the relationship between the microstructure and critical current density J(c) values, are discussed in this paper.