The applications of niobium-titanium cryogenic superconducting alloys are indeed very extensive, ranging from large-scale scientific research facilities to medical equipment, and in cutting-edge transportation and energy fields, where they are key materials.
Large-scale scientific research facilities, such as the Large Hadron Collider at CERN and the Experimental Advanced Superconducting Tokamak (EAST) in China, use niobium-titanium superconducting coils to generate strong magnetic fields to confine and guide particle beams.
Medical magnetic resonance imaging (MRI) Over 90% of medical MRI equipment uses niobium-titanium superconducting coils to provide stable, strong magnetic fields (typically 1.5T-3T, up to 12T in clinical applications), making it a mainstream application.
Cutting-edge transportation and energy Maglev trains use niobium-titanium superconducting coils to generate levitation and propulsion magnetic fields. Superconducting power transmission cables enable high-capacity, low-loss power transmission. Energy storage devices, such as superconducting magnetic energy storage (SMES), are used for grid stabilization. Industrial and scientific equipment includes high-intensity magnetic separators, nuclear magnetic resonance spectrometers, particle accelerators, and high-field laboratory magnets.
Its widespread application stems from its excellent comprehensive performance: a critical temperature of approximately 9.2K, an upper critical magnetic field of approximately 15T, and the ability to be fabricated into flexible wires through conventional processing at a relatively low cost. Although it requires cryogenic cooling with liquid helium (4.2K), its reliability and economy make it irreplaceable in fields with strong magnetic fields and high currents. Niobium-titanium alloys remain key materials in higher-field MRI (e.g., 7T), controlled nuclear fusion, and next-generation particle accelerators, while also being used in synergy with emerging high-temperature superconducting materials to drive technological advancements.
The processing of niobium-titanium cryogenic superconducting alloys is a highly precise, multi-stage metallurgical and mechanical process designed to transform alloy ingots into flexible superconducting wires with high critical current density, excellent mechanical stability, and a uniform microstructure. Its core process follows a standardized industrial route of "melting—cladding—plastic deformation—heat treatment."
High-purity niobium (Nb) and titanium (Ti) are precisely fused at an atomic ratio of 47:53 (approximately 46%–50% Ti by mass) using vacuum arc remelting or vacuum induction melting techniques. The melting process is carried out under an inert atmosphere or high vacuum, with strict control over the content of interstitial elements such as oxygen, nitrogen, and carbon (<100 ppm) to avoid degrading superconducting properties. The melt is cast into cylindrical ingots, followed by homogenization annealing (approximately 1000–1200℃) to eliminate compositional segregation and obtain a uniformly structured initial billet.
The ingots are then hot-forged or hot-rolled into NbTi rods with a diameter of approximately 3–5 mm. An oxygen-free copper (OFC) or high-purity aluminum coating is applied to the outer layer of the NbTi rod as a stabilizing matrix, providing current bypass and preventing thermal superconductivity loss.
Between the NbTi rod and the copper layer, a niobium (Nb) barrier layer (several micrometers thick) is often embedded to inhibit the formation of brittle intermetallic compounds (such as TiCu₄) between Ti and Cu, ensuring the metallurgical bonding strength of the interface.
Multiple coated single-core rods are arranged into a hexagonal honeycomb structure and inserted into a large-diameter oxygen-free copper-clad tube. The gaps are filled with copper inserts, and the tube is sealed by electron beam welding to form a composite ingot.
