Longitudinal Component Resistivities of Multifilamentary Composite Strands — Influences of Size Effect and Filament/Matrix Interdiffusion
Longitudinal resistivity measurements were performed on the electrolytically separated components (shell, interfilamentary matrix, and filaments) of two pairs of un-heat-treated Nb-46.5 wt. %Ti multifilamentary strands (matrices Cu and Cu-0.5 wt. % Mn, respectively) at 295 and 12 K. The measurements were also repeated on the Cu-matrix pair after annealing at 150, 245, and 415°C. It was observed that: (1) The residual resistivity ratio and ρ 12K of the Cu shell of the annealed NbTi/Cu strands ( ≈170 and ≈ 10 nΩcm, respectively) agreed with typical bulk values of OFHC Cu. (2) The Cu-shell resistivities of as-received strands (un-heat-treated) had been enhanced by drawing-induced deformation microstructure. (3) The residual resistivity of the Cu matrix was 4 to 6 times larger than that of the corresponding Cu shell — an enhancement attributable to size effect. (4) Size effect makes a negligible contribution to the resistivity of the Cu-Mn matrix. (5) Annealing at moderate temperatures reduces the shell resistivity; conversely, that of the matrix increases as the annealing temperature is raised above 300°C, presumably as a result of filament/matrix interdiffusion.
KeywordsMatrix Resistivity Filament Diameter Electrolytic Etching Longitudinal Resistivity Residual Resistivity Ratio
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