The effect of hydrostatic extrusion on theJc(B) characteristicof ex situ MgB2 wires

Abstract

MgB2/Fe(Cu) wires fabricated by the PIT method with involvement of the hydrostatic extrusion (HE) processshow a noticeable core homogeneity and refined microstructure which result in high transportJc values.The highest Jc for sintered wire were measured for HE SiC doped wire104 A cm−2 (Fe clad)and 0.5 × 104 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 toJc = 0.4–0.5 × 104 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 significantgrain refinement (individual grains below 200 nm), homogeneity and density within thehydrostatically extruded cores. After deformation by hydrostatic extrusion the enhancedJc at higherfields 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 abimetallic Cu/Fe sleeve. The beneficial effect of hydrostatic extrusion onJc(B) characteristics can be attributed to very high core density in comparison to otherdeformation routes.