Invar ( Fe64/Ni36 )
Controlled Expansion Alloy.
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.
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, valves in motors, etc.) However, it has a propensity to