Editing Invar (section)

{{Short description|Alloy of nickel and iron with low coefficient of thermal expansion}}
{{Use dmy dates|date=February 2023}}
[[File:Invar 800.jpg|thumb|Samples of Invar]]
[[File:Invar-Graph-CTE-composition.svg|thumb|350px|right|The coefficient of thermal expansion of nickel/iron alloys is plotted here against the nickel percentage (on a mass basis) in the alloy. The sharp minimum occurs at the Invar ratio of 36% Ni.]]

'''Invar''', also known generically as '''FeNi36''' ('''64FeNi''' in the US), is a [[nickel]]–[[iron]] [[alloy]] notable for its uniquely low [[coefficient of thermal expansion]] (CTE or α). The name ''Invar'' comes from the word ''invariable'', referring to its relative lack of expansion or contraction with temperature changes,<ref name="alloying">{{cite book | last = Davis | first = Joseph R. | title = Alloying: Understanding the Basics | year = 2001 | publisher = ASM International | pages = 587–589| isbn = 0-87170-744-6 }}</ref> and is a registered trademark of [[ArcelorMittal]].<ref>US Trademark #63970</ref>

The discovery of the alloy was made in 1895 by Swiss physicist [[Charles Édouard Guillaume]] for which he received the [[Nobel Prize in Physics]] in 1920. It enabled improvements in scientific instruments.<ref>{{cite web |title=The Nobel Prize in Physics 1920 |url=http://nobelprize.org/nobel_prizes/physics/laureates/1920/ |work=nobelprize.org |publisher=The Nobel Foundation |access-date=20 March 2011 |quote=The Nobel Prize in Physics 1920 was awarded to Charles Edouard Guillaume ''"in recognition of the service he has rendered to precision measurements in Physics by his discovery of anomalies in nickel steel alloys"''.}}</ref>