Invar, also called FeNi36, is an alloy of iron (64%) and nickel (36%) with some carbon and chromium. This alloy is known worldwide for its unique properties of controlled coefficient of thermal expansion (CTE). It was invented in 1896 by Charles Edouard Guillaume, who later received the Nobel Prize in Physics in 1920. Image File history File links Download high resolution version (928x629, 17 KB) Graph of Coefficient of Thermal Expansion set against nickelcontent of nickel-iron alloy (invar alloy) I created this graph, using data I found in Charles-Edouard Guillaumes Nobel Prize Lecture. ... Alloy is a combination, either in solution or compound, of two or more elements, which has a combination of at least one metal, and where the resultant material has metallic properties. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... General Name, Symbol, Number nickel, Ni, 28 Chemical series transition metals Group, Period, Block 10, 4, d Appearance lustrous, metallic Atomic mass 58. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... General Name, Symbol, Number chromium, Cr, 24 Chemical series transition metals Group, Period, Block 6, 4, d Appearance silvery metallic Atomic mass 51. ... Solids expand in response to heating and contract on cooling; this response to temperature change is expressed as its coefficient of thermal expansion: The coefficient of thermal expansion is used in two ways: as a volumetric thermal expansion coefficient as a linear thermal expansion coefficient These characteristics are closely related. ... Charles Edouard Guillaume ( February 15, 1861 РMay 13, 1938) received the Nobel Prize in Physics in 1920 in recognition of the service he had rendered to precision measurements in Physics by his discovery of anomalies in nickel steel alloys. ... Hannes Alfv̩n, 1970 winner for work on astrophysical plasmas List of Nobel Prize laureates in Physics from 1901 to the present day. ...

Due to its low coefficient of thermal expansion at room temperature (about 10^-6 K^-1 in length; some formulations have negative CTE) it is used in precision instruments (clocks, physics laboratory devices, seismic creep gauges, shadow-mask frames,[1] valves in motors, etc.) However, it has a propensity to creep. The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... A wall clock A clock (from the Latin cloca, bell) is an instrument for measuring time. ... The shadow mask is one of two major technologies used to manufacture cathode ray tube (CRT) televisions and computer displays that produce color images (the other is aperture grille). ... Italic text Italic textBold text Creep is the term given to the material deformation that occurs as a result of long term exposure to levels of stress that are below the yield or ultimate strength, often in combination with temperatures near its melting point. ...

Although Invar is today a widely used material in many industries and applications, this is a particular trademark of a French company named Imphy Alloys: this company originates from the Acieries D'Imphy (a small city near Nevers, France) where the alloy was initially industrialised after its invention. The generic reference for Invar(R) is FeNi36. Nevers is a commune of central France, the préfecture (capital) of the Nièvre département, in the former province of Nivernais. ...

There are variations of the original Invar material that have slightly different coefficient of thermal expansion such as :

• FeNi42 which matches the CTE of silicon and therefore is widely used as lead frame material for electronic components, integrated circuits, ...
• FeNiCo alloys - named Kovar or Dilver P - that have the same expansion behaviour as glass, and because of that are used for optical parts in a wide range of temperatures and applications, such as satellites.

General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance dark gray, bluish tinge Atomic mass 28. ... Kovar is a nickel-cobalt ferrous alloy. ... This article refers to the material. ... A satellite is any object that orbits another object (which is known as its primary). ...

External links

• http://orologeria.com/english/magazine/magazine3.htm