Superconducting Properties of Added RHQT- Wires Through the Clad-Chip Extrusion Method

Fabrication and superconducting properties of Sn added Nb₃ Al wires are presented. The wire fabrication process consists of the clad-chip extrusion (CCE) method and the rapid-heating, quenching, and transformation (RHQT) treatment. The former (CCE) is a metal-composite fabrication method and characterized by the extrusion of thin chips of Nb/Al clad-rolled sheet. It can produce the Sn-adding Nb/Al microcomposite precursor with the intended chemical composition. The latter (RHQT) is a heat-treatment method to transform the precursor to the Nb₃Al wire by way of the bcc-structured supersaturated solid solution, Nb(Al)_ss. It can produce not only the nearly stoichiometric composition but also fine grain of Nb₃Al, which is favorable for upgrading the superconducting properties. The combined process of the CCE method and the RHQT treatment successfully fabricated the Sn added Nb₃Al wires with Sn-addition from 0.25 to 5 atomic percent (at%). Sn-addition to Nb/Al composite wires affected the phase transformation at RHQT treatment. With increasing Sn-addition, the Nb(Al)_ss became unstable and A15 phase was dominant at the stage of rapid-heating and quenching. The RHQT-treated Nb₃Al wire with nearly 2 at% Sn-addition showed the maximum transition temperature Tc but the more addition decreased Tc. The small Sn-addition within 2 at% improved both of the critical field and the critical current density, although the more addition decreased them drastically