Studying the Structure of the Elements of the Cable of Technical Superconductors by Atomic Force Microscopy

摘要

Microstructural evolution in a superconductive cable made of the Nb+47%Ti alloy and drawn to obtain intermediate reduction from Ø1.3 to Ø1.2 mm is studied by atomic force, optical and electron microscopies. This alloy is used for making current-carrying elements in the magnetic system of the International Thermonuclear Experimental Reactor (ITER). The aim of the paper is to analyze the effect of cold deformation by drawing on the structure of a Nb-Ti alloy-based multicore superconductor. The microstructures have been examined, as well as the effect they have on the properties of the cold-drawn superconductive Nb-Ti alloy. The micro structural parameters, such as grain and subgrain sizes, phase and chemical homogeneity of the grains, have been determined. Strain localization zones have been revealed in the sites of wire breakage. Changes in the chemical composition of Nb-Ti wires in defect-free breakage zones have been detected. It has been found that a diffusion Nb barrier is formed around the Nb-Ti wire placed in the copper binder.