Advanced Alloy Superconductor Wire Manufacturing Technology

为了支持基于Nb-Ti合金的多丝超导体中的大电流，超导线中需要一个细小的子结构。为了制造100A量级的子结构，传统的多丝超导体制造技术需要相当多的繁琐的加工步骤。通常，直径为5英寸的Nb-钛合金铸锭通过挤压和拉丝进行机械加工，直到获得直径为5微米的细丝。由于合金元素在凝固过程中的偏析，在初始铸锭中产生的化学不均匀往往对超导体性能有害。提出了一种制备多丝超导体的全新工艺路线，该工艺有可能生产出性能更好、成本更低的超导体。这种方法包括直接从熔体中制备连续的超导丝，通常是40微米厚。当从熔体中提取这种细丝时，其凝固率很高。高的凝固速度导致了化学均匀的组织，具有非常细小的晶粒尺寸和约100A量级的亚结构。该项目将探讨获得理想的磁通钉扎微结构和高临界电流密度的可行性。这种发展将省去所有需要大范围机械变形的加工步骤。还将探索将直接从熔体中制备的超导体长丝并入复合线的方法。这项工作将显著改善精细多丝复合Nb-Ti超导体的性能，并显著降低此类线材的生产成本。该材料将适用于广泛的应用，包括未来高能加速器磁铁的偶极和四极。

To support large currents in multifilamentary superconductors based on niobium-titanium alloys, a fine scale substructure is required within the superconductor wire. To produce substructure of the order of 100A, the conventional multifilamentary superconductor fabrication technology requires a rather large number of tedious processing steps. Typically a 5 inch diameter niobium-titanium alloy ingot is mechanically worked through extrusion and wire drawing, until 5 micrometers diameter filaments are obtained. The chemical inhomogeneity in the starting ingots that arises due to segregation of alloying elements during solidification is often deleterious to the superconductor properties. An altogether new manufacturing route for the preparation of multifilamentary superconductors is proposed, which has the potential of producing superconductors with improved characteristics, and significantly lower cost. The approach involves preparing continuous superconductor filaments, typically 40 micrometers thick, directly from the melt. Such thin filaments, when extracted from the melt experience high solidification rates. The high solidification rates lead to a chemically homogeneous microstructure with extremely fine grain sizes and sub-structures of the order of 100A. This project will address the feasibility of obtaining desirable microstructures for flux pinning and high critical current density. This development will obviate all the processing steps requiring extensive mechanical deformation. Approaches to incorporate the superconductor filaments prepared directly from the melt, into composite wires will also be explored. The work will result in significant property improvements in fine multifilamentary composite niobium-titanium superconductors, and considerable cost reduction in the production of such wires. The material will be suitable for a wide range of applications including dipoles and quadrapoles for future high energy accelerator magnets.