An internal Mg–Li alloy composite process for the fabrication of MgB2wire

This paper proposes a composite process for the fabrication of MgB 2 wire utilizing the excellent room temperature workability of Mg–Li alloy (LA141) as one of the promising processes for scale-up production. The starting composite is a Fe sheath tube with a coaxial internal Mg–Li alloy rod and powder mixture of B and nano-SiC filling the space between the inner wall of the Fe tube and the Mg–Li alloy rod. The composite can be deformed uniformly into the final wire with large cross-sectional area reduction and no intermediate annealing. During the subsequent heat treatment, Mg and Li in the liquid state infiltrate into the B layer and react with B forming a reacted layer along the inner wall of the Fe tube and a hole at the centre. The reacted layer is composed of a MgB 2 matrix composed of equi-axed grains with sub-micron size. Li is little incorporated into the MgB 2 phase and does not degrade the superconducting properties. The superconducting transition temperature T c is 38 K and the transport critical current density J c (core) for the core is 3 × 10 4 A cm −2 at 4.2 K and 4 T.