Nickel-iron alloy

An iron–nickel alloy or nickel–iron alloy, abbreviated FeNi or NiFe, is a group of alloys consisting primarily of the elements nickel (Ni) and iron (Fe). It is the main constituent of the "iron" planetary cores and iron meteorites. The acronym NiFe refers to various chemical reactions that involve an iron–nickel catalyst or component, or in geology, to the general composition of planetary cores (including Earth's).

Some iron–nickel alloys are called nickel steel and usually contain additional elements, depending on the purpose.

Iron and nickel are notable for being the final elements produced by stellar nucleosynthesis, and the heaviest elements formed with a supernova or similarly cataclysmic event. Iron and nickel are the most abundant metals in metallic meteorites and in the dense metal cores of planets such as Earth.

Nickel–iron alloys occur naturally on Earth's surface as telluric or meteoric iron.

The affinity of nickel atoms (atomic number 28) for iron (atomic number 26) results in natural occurring alloys and a large number of commercial alloys, and provides a complex electron environment for catalyzing chemical reactions.

In steel metallurgy, nickel is alloyed with iron to produce maraging steel and some low-alloy steels. Other technological uses include Invar and Mu-metal.

...
Wikipedia