Comparison of mechanical and superconducting properties of titanium-added Nb3Sn composite wire with those of non-added ones

The mechanical and superconducting properties of Ti-added Nb 3 Sn superconducting composite wire were studied experimentally and the results were compared with those of non-added ones. When titanium was added, the growth rate of the Nb 3 Sn compound was enhanced. The grain size of the compound was reduced when the annealing temperature was high but not when it was low. The fracture behaviour of Ti-added specimens was essentially the same as that of non-added ones: when the amount of Nb 3 Sn was small, the specimens showed large apparent plastic deformation; when it was large, the specimens showed brittle fracture without apparent plastic deformation, but the strength of the Nb 3 Sn compound was different between the Ti-added and non-added specimens. The strength of the Ti-added compound was lower than that of non-added ones. Although the strength of the Nb 3 Sn was different, the strength of both Ti-added and non-added compounds was nearly proportional to the inverse root grain size. The global pinning force of both compounds was proportional to the product of the inverse grain size and f(H,H c2 ) which is a function of the applied magnetic field and upper critical magnetic field. The global pinning force was raised by the addition of titanium especially at high magnetic field due to an increase in the upper critical magnetic field.