Superconducting properties of Nb_3Al wire fabricated by the clad-chip extrusion method and the rapid-heating, quenching and transformation treatment

摘要

The study of a fabrication process for Nb_3Al intermetallic compound wire and measurements of its superconducting properties are presented. The adopted process of fabrication for the superconducting wire consists of the clad-chip extrusion (CCE) method and the rapid-heating, quenching and transformation (RHQT) treatment. The former (CCE) is the processing of Nb/Al composite wire characterized by the extrusion of thin chips of Nb/Al clad-sheet in which the thickness ratio of the Nb-layer to the Al-layer corresponds to Nb_3Al. The latter (RHQT) is the heat-treatment method to transform the CCE-processed Nb/Al composite wire into the Nb_3Al intermetallic compound, which gives a nearly stoichiometric composition and a fine grain of Nb_3Al for high performance of superconductivity. The experimental results show that the wire is successfully fabricated by the CCE method and the RHQT treatment, and its superconducting properties are improved to 18.02 K of T_c and 318 A/mm~3 of J_c at 20 T and 4.2 K. It is also shown that 26.3 T of H_(c2) is estimated by a Kramer plot.