The effect of hydrostatic extrusion on the Jc(B) characteristic of ex situ MgB2 wires

MgB2/Fe(Cu) wires fabricated by the PIT method with involvement of the hydrostatic extrusion (HE) process show a noticeable core homogeneity and refined microstructure which result in high transport J(c) values. The highest J(c) for sintered wire were measured for HE SiC doped wire 10(4) A cm(-2) (Fe clad) and 0.5 x 10(4) A cm(-2) (Cu/Fe clad), both at 4.2 K and 5.5 T. Combination of HE with two-axial rolling (TAR) has led to J(c) = 0.4-0.5 x 10(4) A cm(-2) at 4.2 K and 5.5 T. High n-exponent values (between 21-110 at 4.2 K and 5.5 T) prove significant grain refinement (individual grains below 200 nm), homogeneity and density within the hydrostatically extruded cores. After deformation by hydrostatic extrusion the enhanced J(c) at higher fields for pure MgB2 and MgB2 SiC nano-doped wires in comparison to only TAR wires were measured. Wires sheathed with Fe gave better results than those sheathed with a bimetallic Cu/Fe sleeve. The beneficial effect of hydrostatic extrusion on J(c)(B) characteristics can be attributed to very high core density in comparison to other deformation routes.