Influence of parent Nb-alloy grain morphology on the layer formation of Nb3Sn and its flux pinning characteristics

Abstract

The influence of parent Nb-alloy grain morphology on the layer formation of Nb3Sn and its pinning characteristics was clarified using a fundamental method. Nb–Ta–Hf was used in this work, given its high recovery temperature of more than 700 °C, which is higher than the Nb3Sn-phase formation temperature. First, a Cu/Nb–4at%Ta–1at%Hf single-core composite wire (outer: Cu) was prepared. Subsequently, two pieces were cut off, one of which was intermediately annealed at the recrystallization temperature. Thereafter, Sn was attached onto the surface of both the samples by electroplating, and the samples were heat-treated for Nb3Sn layer formation. Evidently, a significantly finer grain morphology appeared on the as-drawn fine parent Nb-alloy layer, leading to a much better pinning force property.