Microstructural and compositional gradients in the filament-matrix region of Nb-Ti wire composites

Author

Faase, K.J. ; Warnes, W.H. ; Lee, P.J. ; Larbalestier, D.C.

Author_Institution

Dept. of Mech. Eng., Oregon State Univ., Corvallis, OR, USA

Volume

5

Issue

2

fYear

1995

fDate

6/1/1995 12:00:00 AM

Firstpage

1197

Lastpage

1200

Abstract

Transverse cross-sections of Nb-Ti wire composites after final /spl alpha/-Ti precipitation heat treatment (10-480hr/420/spl deg/C) were examined and analyzed in the filament-matrix region with scanning electron microscope-backscatter electron imaging (SEM-BEI) and electron micro probe analysis (EMPA). SEM-BEI micrographs were image analyzed to quantify the average effective /spl alpha/-Ti precipitate diameter, d*, and volume fraction of /spl alpha/-Ti as a function of distance into the filament. Cu concentration profiles were found in the same regions by EMPA. The compositional results show trace amounts of Cu (>0.1 at%) interdiffused up to 50 /spl mu/m into the Nb-Ti filaments. The interdiffused Cu at the interface increased /spl alpha/-Ti nucleation and thus increased /spl alpha/-Ti volume fractions by 50% relative to the nominally pure Nb-Ti at the center of the filament for short heat treatment times (30 hours of total heat treatment time).<>

Keywords

chemical interdiffusion; crystal microstructure; electron backscattering; electron probe analysis; heat treatment; multifilamentary superconductors; niobium alloys; nucleation; precipitation; scanning electron microscopy; titanium alloys; /spl alpha/-Ti precipitation heat treatment; /spl alpha/-Ti volume fractions; 10 to 480 hour; 420 degC; Cu concentration profiles; Cu interdiffusion; EMPA; Nb-Ti wire composites; NbTi-Cu; average effective /spl alpha/-Ti precipitate diameter; composite superconductor; compositional gradients; electron microprobe analysis; filament-matrix region; microstructural gradients; nucleation; scanning electron microscope-backscatter electron imaging; short heat treatment times; transverse cross-sections; Etching; Heat treatment; Image analysis; Mechanical engineering; Microstructure; Niobium; Probes; Scanning electron microscopy; Transmission electron microscopy; Wire drawing;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/77.402776

Filename

402776