Mechanical and critical current characteristics of high-strength Bi 2 Sr 2 Ca 2 Cu 3 O 10+δ multi-filamentary tapes reinforced with thicker Ni-alloy laminations with various pre-tensions

Abstract

We investigated the stress–strain relation and the applied strain dependence of critical current I c(ε app) of high-strength Bi2Sr2Ca2Cu3O10+δ (Bi2223) R&D tapes reinforced by ~100-μm-thick Ni-based alloy sheets with various pre- tensions F pre applied during a lamination process. We confirmed that the thickening of Ni-alloy laminations is useful to enhance Young’s modulus compared with commercial tapes (≈30-μm-thick laminations). I c(ε app) decreases gradually and reversibly with applied strains ε app and then degrades irreversibly with larger tensile and compressive strains. The reversible strain regime tends to shift towards the tensile side with larger F pre, indicating that application of large F pre is effective to improve the reversible tensile strain limit. Observed I c(ε app) can be reproduced well by the model considering an ε app-linear critical current density, a cross-sectional strain distribution, and a Weibull-type distribution of filament damages. We clarified that different irreversible I c(ε app) degradations with large tensile and compressive strains can be understood by differences in the dimension and number of cracks and ruptures (tensile strains) and bucklings (compressive strains).