The research on the influence mechanism of internal deformation for the performance of Bi-2212

Abstract

CICC (Cable-in-conduit conductor), one of the most promising forms of magnets in magnetic confinement fusion devices, has attracted lots of attention. In the production of CICC, porosity control is necessary for its stability. The porosity control is usually realized by diameter reducing process, which would also lead to indentation damages to the elements of CICC-superconducting wires. In this article, systematic research of indentation damages was carried out on the next generation of high-temperature superconducting materials-Bi2212 wires. The results indicate that the current carrying capacity of the indentation-damaged wire would first keep steady and then show exponential decline with the increase of indentation depth. While the pre-over pressure treated wires show better resistance to indentation damages: its Ic would show a decreasing trend in higher indentation depth compared with the original wires. The following structural characterization analyzed the reasons for the property changes with the help of SEM, CT, and hardness tester. The results indicate that the increased angle of the grain boundary leads to the exponential decline in Ic. In the meantime, the differences in properties of the two kinds of wires result from the differences in crystal structures originating from the mechanical changes of the pre-OP heat-treated wires.