Structure and superconducting property characterisation of MF Cu/Nb - 46.5 w% Ti superconductors

Optical microscope-, SEM-, TEM- and AES-facilities were used to comprehensively characterise metallurgical structures of composites comprising of 60 Nb-47.1 w% Ti filaments embedded in copper matrix and having various thermomechanical treatment histories. Superconducting properties were measured at temperatures of 4.24 K and 2.50 K at magnetic fields up to Bc2. At 4.2 K, an optimum microstructure produces technically interesting high critical current carrying capacities at low, mid and high magnetic field regimes, and at 2.5 K the critical current densities suggest utility of nominal 46.5 w% Ti alloys at magnetic fields up to 11 T. The improvements in superconducting properties are associated with refinement of well defined sub-band boundaries to an optimum spacing of 20 nm, whereas extensive final cold working results in distorted microstructure having additional dislocation related diffuse boundaries and, consequently, an impaired superconducting performance at low and mid magnetic field regimes.