Invar

Background information: Invar is an alloy of nickel and steel, or specifically know as FeNi36, which means Nickel-Steel 36. In US, it is the opposite, 64FeNi. The "36" actually means 36%, which refers to the percentage of nickel at which Invar is expands the least when heated, same goes for the American version, meaning a 64% steel composition. Invar was invented by Charles Edouard Guillaume, a Swiss scientist, in the year 1896. In 1920, for this discovery, he won the Nobel prize in Physics, due to the great improvements imposed by this material on scientific instruments. (Koh Han Wei)

Charles Edouard Guillaume and Invar
Most metals and alloys, including steel, expand significantly when they’re heated. Engineers work around this; for example, they build expansion joints into bridges. But there are many situations in which it is so much better if the material expands hardly at all. Charles Edouard Guillaume discovered such a material. Swiss-born physicist Guillaume spent most of his working life at the International Bureau of Weights and Measures in Sèvres, France. One project he was involved with had to do with trying to establish an international standard for the meter, the metric unit of length. Today, the meter is defined as the length of the path traveled by light in a vacuum in 1/299,792,458 of a second. During Guillaume’s career in the late nineteenth century, however, a standard was a particular metal bar known as a prototype. Replicas were calibrated to the prototype and distributed to where they were needed. In 1889, an international convention adopted a new prototype for the meter made of platinum and iridium. It was hard and durable, and the most precise prototype yet—but it was outrageously expensive. This troubled Guillaume, because the price of a replica put it out of reach of most scientists, and he resolved to seek a less costly solution. His work led to the discovery of a fairly inexpensive iron-nickel alloy—a steelike material—that expands very little when heated. He named the alloy //Invar// because it was almost unchanging or "invariable." It has the lowest thermal expansion of metals and alloys at temperatures ranging from room temperature to more than 200 degrees Celsius.

Although Invar was never used as a meter prototype, it’s been put to work in standards for length measurement used by surveyors. It’s also used in a vast number of temperature-sensitive devices. In today’s home, for instance, you’ll find Invar in toasters, irons, and gas stoves, as well as in CRT computer monitors and TV sets. In 1920, Charles Edouard Guillaume was awarded the Nobel Prize in physics "in recognition of the service he has rendered to precision measurements in physics by his discovery of anomalies in nickel steel alloys."

First published 2 January 2007 Source: []