Strain Dependence of Critical Current for Nb₃Al Superconducting Wire Fabricated by Restacked RHQT Process

Abstract

Stress/strain dependence of critical current (I c ) was investigated for a restacked rapid-heating, quenching and transformation (RHQT) processed Nb 3 Al superconducting wire consisting of six solid-solution strands. Each strand has 78 filaments with 17.8 μm in diameter. The wire diameter and copper/ non-copper ratio are 0.808 mm and 1.57, respectively. The mechanical properties were measured at 15 T in liquid helium bath (4.2 K) using a strain apparatus that allows stress-free cooling of the sample. I c reached a maximum value of 175 A at an applied strain of 0.09% indicating that Nb 3 Al filaments are under a precompressive strain of a similar magnitude. I c reversibility was confirmed up to 0.3% tensile strain, suggesting that the intrinsic irreversible strain limit is at least as high as 0.2%.