Invar: history of discovery, properties and applications

The history of science and technology is rich in many significant discoveries, including the creation of invar, an alloy of iron and nickel. This material has a unique physical property — almost zero thermal expansion coefficient.

The creation of the invar was an important achievement in physics and materials science, opening up new perspectives in the technology and production of precision instruments. The alloy remains relevant and in demand today, playing a key role in modern technologies and scientific research.

The history of the discovery of invar

Charles Eugene Guillaume (1861—1938) was a famous French physicist and metrologist. At the end of the 19th century, he worked on the problem of creating a length standard that did not depend on temperature. The length standard was necessary for the development of science and technology, as well as for ensuring the accuracy of measurements in industry and commerce.

Guillaume conducted a series of experiments with various materials and found that an alloy consisting of nickel et gland, has a unique property — its temperature coefficient of linear expansion (TKLR) very small and almost independent of temperature. This material is called invar. In 1920, Charles Guillaume was awarded the Nobel Prize in Physics for his discovery of invar, from which it became possible to manufacture precision instruments and devices.

Features of invar properties

Invar is a material that mainly consists of nickel (its mass fraction is about 36%) and iron (contained in an amount of about 64%). The melting point of the material is +1425°C, the density is 8130 kg/m³.

The main physical properties of invar are:

• very low coefficient of thermal expansion — about 1.2×10°C°C¹;
• high strength — in the hardened state, the tensile strength of the tape is 930 MPa in accordance with GOST 14080-78.

The effect of the disappearance of thermal expansion occurs due to the compensation of TCLR by magnetostriction. That is, when the material is magnetized and demagnetized, its linear dimensions and volume change, which compensates for thermal expansion.

The use of invar

Due to its unique properties, invar is widely used in various fields of industry and science:

• Manufacture of precision instruments and tools. Invar is used to make length standards, geodetic instruments, thermometers and other measuring instruments.
• Watch industry. Invar is used in the manufacture of watch mechanisms.
• Medicine. The alloy is used for the manufacture of implants and prostheses, since invar does not cause rejection by the body and is not subject to corrosion.
• Space technology. The properties of the invar do not change under vacuum and low temperatures.
• Microelectronics. Chip substrates, laser surfaces, and waveguides are made from the invar.

The alloy has increased strength and elasticity, which makes it possible to manufacture complex structures and mechanisms from it. In addition, invar can be used to produce parts of all sizes and shapes, including single copies.

Alloys with a specified TKLR produced by PZPS

PZPS produces not only invar (36N), as well as other alloys with a given temperature coefficient of linear expansion, including, 29NK et 42N. We are also engaged in development of new materials and production technologies in accordance with the technical requirements of customers. For cooperation and the purchase of precision alloy tapes of the required thickness and width, please contact specified phone or leave requests on the site. Our staff will contact you and answer your questions in detail.

‍