ASTM B884 Niobium-Titanium Alloy Billets, Bar, and Rod
- Grade: NbTi47, Nb-47Ti, Nb53Ti47
- Superconductivity
- Critical Magnetic Field (Hc)
- Critical Current Density (Jc)
- Ductility and Malleability
- Bar Dia.: ∅10 – 60mm
- Rod Dia.: ∅60 – 150mm
- Billet Dia.: ∅150 – 200mm
Features
ASTM B884 Niobium-Titanium Alloy Bar, Billets, and Rod for Superconducting Applications
Chemical Composition (wt.%) of Nb-47Ti Niobium-Titanium Alloy Billets, Bar, and Rod
| Element Content, Ingot Maximum Limit (ppm) | |||||||||||
| Grade | Al, max | C, max | Cr, max | Cu, max | H, max | Fe, max | Ni, max | O, max | Si, max | Ta, max | Ti, max |
| Nb-47Ti | 100 | 200 | 100 | 100 | 45 | 200 | 100 | 1000 | 100 | 2500 | 46% – 48% |
Room Temperature (RT) Mechanical Properties (~25°C)
| Property | Value | Unit |
| Density (ρ) | 6.0 – 6.4 | g/cm³ |
| Melting Point | ~2,500 | °C |
| Hardness (HV) | 100 – 150 | Vickers |
| Tensile Strength (UTS) | 500 – 700 | MPa |
| Yield Strength (YS, 0.2% offset) | 350 – 500 | MPa |
| Elongation | 20 – 30 | % |
| Elastic Modulus (E) | 50 – 60 | GPa |
| Poisson’s Ratio (ν) | ~0.38 | – |
Cryogenic Temperature Mechanical Properties (~4 K)
| Property | Value at 4K | Unit |
| Tensile Strength (UTS) | 1200 – 1800 | MPa |
| Yield Strength (YS, 0.2%) | 900 – 1200 | MPa |
| Elongation | 5 – 15 | % |
| Fracture Toughness (K_IC) | ~50 – 70 | MPa·m¹/² |
| Elastic Modulus (E) | ~80 – 100 | GPa |
Other Important Properties
| Property | Value |
| Thermal Conductivity (RT, 300K) | 10 – 20 W/m·K |
| Thermal Expansion Coefficient (CTE, 20–300K) | 6.8 – 7.5 × 10⁻⁶ K⁻¹ |
| Electrical Resistivity (RT, 300K) | 70 – 100 μΩ·cm |
| Superconducting Transition Temperature (Tc) | ~9.2 K |
| Critical Current Density (Jc at 5T, 4K) | ~3000 – 5000 A/mm² |
Key Features
Coefficient of Thermal Expansion (CTE): For Nb-Ti alloys, the CTE generally falls in the range of 6.5 × 10⁻⁶ to 8.5 × 10⁻⁶ K⁻¹ (at 20–300 K), depending on the exact composition and temperature range. The value decreases significantly at cryogenic temperatures (below 100 K).
Superconductivity: NbTi47 exhibits superconductivity at cryogenic temperatures, meaning it conducts electricity with zero resistance below its critical temperature (Tc). The Tc of NbTi47 is around 9.2 Kelvin (-263.95 °C).
Critical Magnetic Field (Hc): NbTi47 can withstand relatively high magnetic fields while remaining superconducting. Its critical magnetic field is around 12 Tesla, making it suitable for applications requiring strong magnetic fields.
Critical Current Density (Jc): NbTi47 boasts a high critical current density, meaning it can carry large amounts of electrical current without losing its superconducting state. This property makes it suitable for high-power applications.
Ductility and Malleability: NbTi47 is ductile and malleable, allowing it to be easily drawn into wires or formed into different shapes, which is crucial for practical applications.
Technical Specifications
| Specification | Value |
| Standard | ASTM B884 Niobium-Titanium Alloy Billets, Bar, and Rod for Superconducting Applications |
| Grade | NbTi47, Nb-47Ti, Nb53Ti47 |
| Condition | Soft annealed condition (+A) |
| Type | Bar, Rod, Billet |
| Dimension | Bar diameter: 13 – 60mm Rod diameter: 60 – 150mm Billet diameter: 150 – 200mm |
| Coating | Copper Coating, Nickel Coating, Silver Coating, Titanium Nitride (TiN) Coating, Oxide Coating |
| Inspection Certificate | EN 10204 Type 3.1 (Mill Test Certificate), EN 10204 Type 3.2 (Witness Testing or 3rd Party Inspection) |
| Test | Room / Elevated temperature tension Tests, Chemical Tests |
Manufacturing Process
1. Raw Material Preparation
Niobium and Titanium: High-purity niobium (Nb) and titanium (Ti) are used as raw materials. The composition is typically 47% titanium and 53% niobium by weight.
Alloying: The raw materials are carefully weighed to achieve the desired composition.
2. Melting
Vacuum Arc Melting (VAR): The alloy is melted in a vacuum arc furnace to prevent contamination and ensure homogeneity. The process involves creating an electric arc between an electrode (made of the raw materials) and a water-cooled copper mold. The high temperature of the arc melts the materials, which then solidify into an ingot.
Multiple Melts: The ingot is often remelted multiple times (typically 2-3 times) to ensure uniform composition and eliminate impurities.
3. Forming
Hot Working: The ingot is heated to a high temperature (typically above 1000°C) and hot-worked into billets, bars, or rods using processes like forging, rolling, or extrusion. This step reduces the grain size and improves the alloy’s mechanical properties.
Cold Working: To achieve the desired dimensions for wires and smaller rods, cold working (e.g., drawing or rolling) increases the strength of the material but reduces ductility.
4. Heat Treatment
Annealing: After cold working, the material is annealed to relieve internal stresses and restore ductility. Annealing is typically done in a vacuum or inert atmosphere to prevent oxidation.
Aging (Optional): In some cases, the alloy is aged at intermediate temperatures to optimize its superconducting properties.
5. Finishing
Surface Treatment: The surface of the billets, bars, rods, or wires is cleaned and polished to remove any oxides or contaminants.
Inspection: The final product is inspected for dimensional accuracy, surface quality, and mechanical properties. Non-destructive testing (e.g., ultrasonic testing) may be used to detect internal defects.
6. Wire Drawing (for Wires)
Drawing Process: For superconducting wires, the rods are further drawn through a series of dies to reduce their diameter to the required size (often in the range of micrometers).
Coating (Optional): The wires may be coated with a protective layer (e.g., copper) to improve mechanical stability and electrical conductivity.
7. Quality Control
Chemical Analysis: The composition of the alloy is verified using techniques like X-ray fluorescence (XRF) or inductively coupled plasma (ICP) analysis.
Mechanical Testing: Tensile strength, hardness, and elongation are measured to ensure the material meets specifications.
Packing
Packed in plywood boxes.
Applications
MRI Machines: They help create detailed images of the human body.
NMR Spectroscopy: Used in chemical and biological research.
Particle Accelerators: These are like those at CERN for physics experiments.
Fusion Reactors: Help control plasma for potential energy sources.
Maglev Trains: Enable high-speed, frictionless train travel.
Brain Scanners (MEG): Map brain activity by detecting magnetic fields.
Mass Spectrometers: Analyze chemical compounds with precision.
Rocket and Aircraft Parts: Provide strength and heat resistance in critical components.
Cryogenic Equipment: Suitable for very low-temperature applications like liquefied gas storage.
Electronics and Energy Storage: Superconducting magnetic energy storage (SMES) systems.
Quantum Computing: Essential for creating superconducting qubits in quantum computers.
Power Grids: Superconducting Fault Current Limiters (SFCL).
Geophysics and Neuroscience Tools: SQUIDs (Superconducting Quantum Interference Devices).
