High-strength pearlitic steel-copper composite wires for conductors in pulsed high-field magnets

Pearlitic steel/copper macrocomposite wires were fabricated by the:'rod-in- tube' technology. As a starting material, tubes 25 mm in diameter of patent ed steel with 0.6 wt.% C were used. A composite with 56 vol.% Cu yields an ultimate tensile strength of 1.53 GPa after a final patenting at 14.7 mm di ameter and a logarithmic drawing strain of eta = 4. This high strength leve l is connected with a low elongation to fracture of the order of 1.3-1.5%. Intermediate annealing leads to a solely temporary increase of elongation t o fracture. Therefore, annealing cannot contribute to improving the formabi lity at high strength level. The evolution of strength as a function of dra wing strain was discussed including the model of Embury and Fisher. Assumin g homogeneous strain the postulated proportional decrease of the interlamel lar spacings of the pearlitic cells with the wire diameter takes place only after high drawing strains. A distribution of interlamellar spacings can b e expected after heavy deformation depending on the initial orientation dis tribution of the pearlitic cells. (C) 2001 Elsevier Science B.V. All rights reserved.