Superconductivity is a fundamental phenomenon in physics in which a material acquires zero electrical resistance when it reaches a certain temperature, called the critical superconductivity temperature.
Superconducting (cryogenic) alloys are specially developed materials that have superconducting properties within certain temperature ranges at a given electric charge flux density, magnetic field strength and intensity. They are characterized by high resistance to external factors under three conditions:
- Operating temperature does not exceed the critical temperature at which the transition from the superconducting state to the normal state occurs.
- Magnetic field parameters below the upper critical value.
- Electric current density less than the critical value (determined at a temperature lower than the transition temperature).
Superconducting precision alloys can be cold drawn after preliminary heat treatment, as well as hot deformation, but within strictly defined temperature ranges.
Superconducting precision alloy grades
The group of cryogenic materials presented includes seven alloys: 35BT, 50BT, 65BT, 70TM, 70TM-VD, BTC and BTC-VD. Let's consider the most popular ones:
- 35BT — the alloy is based on titanium (from 60% to 64%) and niobium (at least 33.5% and not more than 36.5%); zirconium (1.7-4.3%) acts as an alloying additive. The metal is characterized by a high specific viscosity, as well as a weak dependence of conductive properties on the dimensions of the products manufactured from it.
- 65BT — the composition contains the same chemical elements as 35BT, but in different proportions: Ti — 22-26%, Nb — 63 — 68%, Zn — 8.5-11.5%. It has the highest critical current density and magnetic field density. It is characterized by an increased yield strength and tensile strength. It is widely used for the manufacture of internal core elements.
- BTZ-VD — a precision alloy based on niobium (from 98.76% to 99.73%) alloyed with titanium (0.07-0.2%) and zirconium (0.2-1%). It is resistant to atmospheric corrosion and oxidation in aggressive chemical environments. The method of manufacture is vacuum-arc melting.
- 70TM-VD — titanium-molybdenum steel alloyed with iron. The percentage of chemical elements is: Ti — 73-76%, Mo — 24-26%, Fe — no more than 2.5%. It has a high resistivity, which changes slightly when the temperature rises or decreases in the range from -289.15°C to -249.15°C.
In the markings of the presented steels, the letter B indicates the presence niobium, and the numbers in front of it are by its percentage. The letter T speaks of the presence in the alloy titanium, C — zirconium, M — molybdenum. Letters VD at the end, the names of materials mean the method of their smelting (vacuum-arc).
Properties of cryogenic precision alloys and their applications
Superconducting precision alloys have a number of unique physical and mechanical characteristics that make them attractive for various fields of industry and technological research. For example:
- Medical equipment — superconducting materials are used to create highly sensitive equipment for magnetic resonance imaging (MRI) and magnetoencephalography (MEG). They make it possible to create powerful magnetic fields with minimal energy loss, which improves the quality and resolution of medical images and makes it possible to more accurately diagnose diseases.
- Quantum computing — the presented alloys have a high potential for creating quantum bits (qubits) in quantum computers. The increased accuracy of physical and mechanical properties and resistance to external factors make such steels promising “candidates” for implementing stable quantum operations.
- Transportation — The ability to create powerful magnetic fields makes superconducting metals suitable materials for creating magnetic fast transport systems, such as magnetoplanes — magnetic cushion trains.
- Energy — the use of superconducting alloys in power systems can increase the efficiency and reliability of electricity transmission, as well as reduce losses during the transmission of electricity over long distances.
- Research in physics — The presented materials are widely used in physical experiments that require the creation of powerful magnetic fields to study the properties of various materials and phenomena.
Despite their many advantages, superconducting precision alloys also have some disadvantages. One of them is the complexity of production and the high cost of the chemical elements that make up the composition. However, research in this area continues, and scientists are constantly looking for new ways to improve the properties and reduce the cost of superconducting materials.
