NbTi superconductors with variable compositions produced by diffusion reaction of niobium and titanium sheets

Three different compositions of NbTi wires have been fabricated by using alternately pure Nb and Ti sheets with Ti contents from 42.5% to 56.6% by adjusting the relative thickness of the Nb and Ti sheets in the monofilaments. Two kinds of heating treatments were discussed and the Nb/Ti interface microstructure and diffusion morphology of cross-section have been investigated by scanning electron microscopy (SEM). The results show that the J_c values are 2800 A/mm² at 5 T/4.2K and 4200 A/mm² at 3 T/4.2 K. With the increase of Ti content, Jc is higher at low magnetic fields (< 5 T), but lower and decreasing rapidly at high magnetic fields. J_c decreases slight slowly for the lower Ti samples. At a given temperature, higher J_c can be gotten by using shorter time of heat treatment for the higher Ti samples, and by using longer.