Effects of Alloying on the Strain Response of Critical Currents in Nb3Sn Conductors

Abstract

In recent years an explanation of the strain tolerance of Nb3Sn conductors has evolved that is based upon an understanding of the composite nature of these materials, specifically, the presence of residual strains in as-fabricated wires [1]. Residual compressive strains, which are induced by thermal contraction of the matrix, exist on the A15 compound and must first be overcome by applied strains, e, before significant degradation in critical current, Jc, can occur. The amount of compressive strain present in as-fabricated conductors varies with factors such as the volume ratio of matrix to filament, R v, and any accommodating plastic deformation that may occur in the matrix or filament during cooldown from heat-treatment temperatures. The results of critical current measurements as a function of tensile and bending strains on monofilament wires alloyed to improve their tolerance to mechanical straining are presented.