Influence of heat treatment strain parameters on the structure and Jc of Nb-48.5 wt.% Ti superconductor

摘要

A multistage heat treatment has been used to form a homogeneous heterophase structure in the Nb-48.5wt.% Ti alloy. The fixed parameters of this treatment were the following: the number of annealings was 4, the temperature and total duration were 390°C and ～400 hours respectively. The degree of plastic strain between consecutive annealings changed across a wide range (εint= 0.1-1.22). The wire drawing schedule was chosen with both equal and unequal values of εint. The values for the final strain, εfin, ranged from 2.3 to 5.6. When equal values of εint were used, the level of Jc obtained in the superconductor was 3640 A/mm2 (at 5 T, 4.2 K). When unequal values of εint where used in the deformation schedule the Jc achieved 3840 A/mm2. TEM was used to quantitatively evaluate the degree of diffusional decomposition in a supersaturated solid solution at different stages of alloy treatment.