Influence of Ti and Ta doping on the irreversible strain limit of ternaryNb3Sn superconducting wires made by the restacked-rod process**Contribution of NIST, an agency of the US government, not subjected to copyright.

Abstract

Nb3Sn superconducting wires made by the restacked-rod process (RRP®) were found to have a dramatically improved resilience to axial tensilestrain when alloyed with Ti as compared to Ta. Whereas Ta-alloyedNb3Sn in RRP wires showed permanent damage to its current-carrying capacity (Ic) when tensioned beyond an intrinsic strain as small as 0.04%, Ti-dopedNb3Sn in RRP strands exhibits a remarkable reversibility up to a tensile strain of about 0.25%,conceivably making Ti-doped RRP wires more suitable for the high field magnets used inparticle accelerators and nuclear magnetic resonance applications where mechanical forcesare intense. A strain cycling experiment at room temperature caused a significant drop ofIc in Ta-alloyed wires, but induced an increase ofIc in thecase of Ti-doped strands. Whereas either Ti or Ta doping yield a similar enhancement of the upper criticalfield of Nb3Sn, the much improved mechanical behavior of Ti-alloyed wires possibly makes Ti a betterchoice over Ta, at least for the RRP wire processing technique.