Ductile superconducting Cu-rich alloys containing A-15 filaments

A new approach to a ductile composite of Cu and an A-15 superconducting compound has been reported recently. This new metallurgical process consists of melting the constituent elements and subsequent cold-working and heat treatment. The superconducting materials prepared by this technique are composed of about 90 atomic per cent Cu and a superconducting compound such as Nb
3
Sn or V
3
Ga which is in the form of fine filaments embedded in the Cu matrix. The new alloy is superconducting at a temperature nearly identical to that of the superconducting phase in bulk form. The current density (J
c
) is
\sim10^{4}
to 10
⁵
A/cm
²
at 4.2°K and zero magnetic field (J
c
is calculated by taking the total cross-section of the specimen). An up-to-date account of the experimental situation in this field will be given. The discussion includes (1) the results of varying the alloy composition, the amount of cold-working and the heat treatment; (2) the transition temperature and J
c
of Sn-coated Cu-(Nb
3
Sn) wires; (3) J
c
as a function of transverse magnetic field; (4) the phenomenon of J
c
enhancement as a result of mechanical deformation and (5) the basic mechanisms responsible for the observed superconductivity in these new materials.