Comparison of phase transformation and superconducting properties of RHQT Nb3Al wires fabricated at Tc peak and valley condition. (October 2019)

• Record Type: Journal Article
• Authors: Xia, Lian; Sun, Xiaguang; Li, Pingyuan; Yu, Zhou; Chen, Yongliang; Zhang, Yong; Pan, Xifeng; Yan, Guo; Feng, Yong; Zhao, Yong
• Is Part Of: Cryogenics. Volume 103(2019)
• Publication Date: 2019-10
• Subjects: Nb3Al wires -- Rapid heating -- Phase transformation -- Annealing temperature -- Grain boundary pinning; Low temperature engineering -- Periodicals; Low temperature research -- Periodicals; 536.56
• DOI: 10.1016/j.cryogenics.2019.102974
• Languages: English
• ISSNs: 0011-2275

Abstract

Highlights: Phase transformation of Nb3 Al wires RHQ at the Tc peak and valley was compared. Nb3 Al wires annealed at 800 °C get the highest T c and Jc when RHQ at the Tc peak. Annealed at 900 °C can get best T c and Jc of Nb3 Al wires quenched at the Tc valley. Abstract: This work compared the phase transformation feature and superconducting properties of Nb3 Al wires rapidly heated at 272 A and 315 A, closing to the Tc peak and valley current condition, respectively. The fabricated rapidly heating, quenching and transformation (RHQT) Nb3 Al wires are mainly consisted of A15 phase with trace Nb and Nb2 Al impurity phase. With the increase of annealing temperature from 700 °C to 1100 °C, the T c value and J c performance of Nb3 Al wires improve first and then gradually decrease. M-T and J c- H curves reveal that the best T c and J c performance of 272 A samples was obtained at the annealing temperature of 800 °C, compared to that of 900 °C for the 315 A samples. In both 272 A and 315 A samples, lower annealing temperature cannot promote the phase transform process from bcc to A15 phase. Excessive heating beyond 1000 °C caused the already transformed Nb3 Al phase to decompose into Nb2 Al and Al-poor Nb3 Al phase, resulting in degraded T c and J c performance of the Nb3 Al wires. The main pinning mechanism of Nb3 Al wires was grain boundary pinning, as deduced from the fitting of flux pinning force versus applied field curves.