Morphology and Structure of Diffusion Layers in Nb₃Sn-Based Superconductors of Different Geometry

Abstract

The evolution of structure and morphology of superconducting Nb3Sn layers forming under various regimes of the diffusion annealing in multifilamentary Nb/Cu–Sn superconductors of different design is briefly reviewed based on the authors’ (with their coauthors) original studies and the available publications. Different modes of the solid-state diffusion formation of the superconducting phase are compared. Possible mechanisms of the Nb3Sn nucleation upon the diffusion reaction of the Nb filaments and bronze matrixes are discussed. The effects of different doping elements, especially Ti, on the formation of the superconducting phase, its structure and morphology, and, consequently, on the current-carrying capacities of multifilamentary Nb3Sn-based wires are considered. Special attention is paid to the effect of the mode of Ti doping, the content of this alloying element and the regimes of the diffusion annealing on the structure, morphology and resulting performance of the bronze-processed wires with coupled Nb filaments worked out at Bochvar Institute of Inorganic Materials for the creation of International Thermonuclear Experimental Reactor.

Insights on grain boundary effects on crack formation and propagation in Nb3Sn coatings at low temperature and high strain rates: a molecular dynamics simulation study

“…We used the Voronoi tessellation method to construct the polycrystalline model, with an average grain size of about 50 nm. The grains were periodically repeated in three coordinate directions, with their centers and orientations randomly distributed, consistent with the typical grain size range (30-200 nm) observed in Nb 3 Sn coatings used for SRF applications [32,33].…”

Effect of Intermediate Heat Treatment on the Formation and Structure of Superconducting Layers in Multifilamentary Nb₃Sn- Based Wires

“…One can judge on the relative amounts of the zones of different morphology only from transverse sections or fractures of the wires [11], which was out of the framework of this study. However, in the longitudinal sections studied by TEM the areas of three types, fine equiaxed grains, coarse grains and elongated (columnar) grains, are observed in all the samples (Fig.…”

Statistical Analysis of Histograms of Grain Size Distribution in Nanostructured Materials Processed by Severe Plastic Deformation

“…The smallest grain sizes that can be achieved by severe plastic deformation (SPD) were observed mainly in materials processed by the high-pressure torsion (HPT) [6][7][8][9][10][11]. Another example of materials with a homogeneous nanostructure is Nb 3 Sn composites in which a structure with similar characteristics is formed by annealing performed after large deformations in accordance with the technology of their production [12][13][14]. In all these works, the results are represented as histograms of size distribution of grains.…”