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A Study on the Adaptability of NbTi Superconducting Alloy to Pulsed High Magnetic Field Conditions, Comparing it with Nb₃Sn, Tungsten, Molybdenum, Tantalum, and C103
Pulsed high magnetic field test devices and short-duration high-energy superconducting pulse magnets need to operate stably under extreme conditions such as millisecond-level strong current impacts, instantaneous strong magnetic fields, rapid temperature changes, and pulsed alternating stress. This requires materials with strong resistance to instantaneous thermal shock, high magnetic flux pinning ability, high pulse current carrying capacity, and low quenching failure. Traditional metals cannot withstand pulsed high-energy impacts; conventional titanium alloys and stainless steel have poor thermal stability; Nb₃Sn is brittle and prone to cracking under pulsed conditions; tungsten and molybdenum have insufficient thermal shock resistance; and pure tantalum and C103 lack superconducting properties. NbTi niobium-titanium alloy, with its excellent pulse current withstand capability, rapid stress relaxation characteristics, and stable magnetic flux pinning performance, has become the core superconducting material for small-to-medium power pulsed high magnetic field devices. In terms of adaptability to pulsed dynamic conditions, it is comprehensively superior to various rare superconducting and refractory metals.
Conventional metals are completely unsuitable for pulsed high magnetic field dynamic conditions. Iron-based alloys and stainless steel exhibit severe eddy current heating under pulsed magnetic fields, resulting in excessively high instantaneous temperature rise and rapid structural thermal failure. Titanium alloys Ti6Al4V and TA2 lack superconductivity, have high eddy current losses, and cannot withstand pulsed superconducting currents. Copper and aluminum conductors are easily ablated under high pulsed currents and exhibit extremely poor thermal stability. All common metals suffer from fatal defects such as high eddy current losses, weak thermal shock resistance, and lack of superconductivity, making them completely unsuitable for pulsed superconducting magnet devices.
This paper repeatedly compares the pulsed magnetic field adaptability of Nb₃Sn, tungsten, molybdenum, high-purity tantalum, and C103 niobium alloys. Nb₃Sn exhibits excellent static high-field superconductivity, but it is highly susceptible to microcracks under pulsed transient thermal shock, and its performance rapidly degrades after multiple pulse cycles. Its brittle defects are amplified under dynamic conditions. Tungsten and molybdenum are heat-resistant and thermally stable, but lack superconductivity and are highly susceptible to brittle cracking under pulsed stress. Pure tantalum is tough and impact-resistant, but lacks superconductivity and can only be used as a thermal insulation structure. C103 niobium alloy is thermally shock resistant and impact-resistant, but lacks superconducting transition and cannot withstand pulsed superconducting current. Compared to all rare metals, NbTi alloys possess superior plasticity and rapid stress relaxation, allowing for rapid release of pulsed alternating stress. They exhibit stable flux pinning centers and show no loss of quench or performance degradation after multiple pulsed impacts, making them far superior in dynamic adaptability.
Within the niobium-titanium superconducting system, commercially available multi-filament composite NbTi is best suited for pulsed conditions. Single-core NbTi wire exhibits severe flux jumps, making it highly susceptible to quench loss under pulsed conditions. NbTi wire without a copper matrix suffers from poor heat dissipation, making it prone to ablation under high pulse temperatures. A novel copper-stabilized NbTi composite structure can rapidly dissipate residual heat from pulses, suppressing temperature rise and significantly improving pulse tolerance. Optimized NbTi pulse magnets can withstand tens of thousands of millisecond-level high-current pulse impacts with a critical current decay rate of less than 3%, exhibiting no cracks or deformations and dynamic stability far exceeding other superconducting candidate materials.
Currently, NbTi pulsed superconducting magnets are being used in batches in scientific research pulsed high magnetic field testing equipment and small-scale high-energy pulsed electromagnetic devices, replacing traditional brittle superconducting materials. This results in a 6-fold increase in equipment pulse cycle life and a significant improvement in operational stability. The material's weakness lies in its insufficient static high-field performance, making it less suitable for ultra-high-field pulsed conditions above 10T compared to Nb₃Sn. Future developments will focus on enhancing NbTi's high-field pulse carrying capacity through nano-precipitation strengthening and composite heat dissipation structure design, consolidating its dominant position in the field of small- and medium-power pulsed superconducting equipment.
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