Improved J/sub c/ in mechanically fabricated Nb3Al wires and ribbons

Nb3Al wire which is essentially all Al5 may be fabricated by powder or rod composite techniques, with subsequent reaction and ordering anneals. Several of the previously existing problems, including aluminum loss and Kirkendall porosity, have been identified and solved, and transverse-field critical current densities well into the 105 A/cm2 range can be produced. However, reproducibility of the critical current density seems to depend on reproducible control of grain size. The internal oxidation techniques which succeed for Nb3Sn do not appear to work for Nb3Al. A possible solution to the grain size problem, and to the problem of manufacture of Nb3Al in stabilized form, is to lower the initial reaction temperature. To achieve the latter, the scale of the elemental composite was reduced to a required diffusion distance of about 3000 A before reaction. Substantial quantities of Al5 could be produced at 11000C, but for several reasons it is believed finer composites will be necessary