Study on Microstructure of Nb-Ti Based Alloy by Groove Rolling Process.

ABSTRACT

Niobium-titanium alloy is attractive materials for industrials as a superconducting magnets to high critical magnetic field and supercurrent density at -283 °C. The Nb-Ti alloy has been shown in earlier work to exhibit Van Gosh Sky microstructures. They may also be accentuated by plastic deformation due to work and temperature exposure during deformation. In order to miniaturize the magnet generating the same magnetic field, it is necessary to increase the critical current density of the superconducting wire. When fabricating superconducting wires, it is important to increase critical current density by optimizing processing and annealing conditions. When the α-phase of the Ti rich phase is uniformly precipitated by the heat treatment, the non-superconducting α-phase is dispersed in the superconducting Nb-Ti matrix. It becomes a pinning point that serves to fix the magnetic flux, which improves the critical current density. Also, if the shape of the precipitate is changed by machining, the superconducting and non-superconducting characteristics are further improved. In the present study, we studied the fraction of α-Ti phase of strain amount through groove rolling and heat treatment. The specimens were processed by groove rolling at room temperature and strain of 2.0, 3.16, 4.28 and 5.57. A microstructural analysis of the Nb-Ti alloys was performed by field emission scanning electron microscopy (FESEM).