MgB2/Fe(Cu) wires fabricated by using the powder-in-tube method and hydrostatic extrusion exhibited a noticeable core homogeneity and a refined microstructure which resulted in high transport JC values. The highest JC for sintered wire was measured for hydrostatically extruded SiC-doped wire 104A/cm2 (Fe clad) and 0.5 x 104A/cm2 (Cu/Fe clad), both at 4.2K and 5.5T. A combination of hydrostatic extrusion with 2-axis rolling led to JC = 0.4–0.5 x 104A/cm2 at 4.2K and 5.5T. High n-exponent values (between 21 and 110 at 4.2K and 5.5T) indicated significant grain refinement (individual grains below 200nm), homogeneity and density within the hydrostatically extruded cores. After deformation by hydrostatic extrusion, the enhanced JC at higher fields for pure and SiC nano-doped MgB2 wires were measured in comparison to only 2-axis rolled wires. Wires sheathed with Fe gave better results than did those sheathed with a bimetallic Cu/Fe sleeves. The beneficial effect of hydrostatic extrusion upon JC(B) characteristics could be attributed to a very high core density in comparison to other deformation routes.

The Effect of Hydrostatic Extrusion on the JC(B) Characteristic of ex situ MgB2 Wires. W.Pachla, P.Kovác, I.Husek, T.Melisek, M.Müler, V.Strbík, A.Mazur, A.Presz: Superconductor Science and Technology, 2005, 18, 552-6