Aniron–nickel alloyornickel–iron alloy, abbreviated FeNiorNiFe, 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. In chemistry, the acronym NiFe refers to an iron–nickel catalyst or component involved in various chemical reactions, or the reactions themselves; in geology, it refers to the main constituents of telluric planetary cores (including Earth's).
Some manufactured alloys of iron–nickel are called nickel steelorstainless steel. Depending on the intended use of the alloy, these are usually fortified with small amounts of other metals, such as chromium, cobalt, molybdenum, and titanium.
Iron and nickel are the most abundant elements produced during the final stage of stellar nucleosynthesis in massive stars. Heavier elements require other forms of nucleosynthesis, such as during a supernovaorneutron star merger.[1][2] Iron and nickel are the most abundant metals in metallic meteorites[3] and in the dense metal cores of telluric planets, such as Earth.
Nickel–iron alloys occur naturally on Earth's surface as telluric ironormeteoric 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. The surfaces of these metallic compounds provide a complex electron environment for catalyzing chemical reactions.[4]
Insteel metallurgy, nickel is alloyed with iron since 1889 (date of Henri Schneider's patent[5] on nickel steel) to produce maraging steel and some low-alloy steels. Other technological uses include Invar and Mu-metal.
The following table is an overview of different iron–nickel alloys. Naturally occurring alloys are a type of mineral and called native elementsornative metals. Some of the entries have more than one crystal structure (e.g. meteoric iron is a mixture of two crystal structures).
| Name | Description | Chemical formula / Weight percent nickel |
|---|---|---|
| Antitaenite | Anintermetallic compound found in meteorites[6] | Fe3Ni |
| Awaruite | Anative intermetallic compound found in serpentinites and meteorites | Ni2Fe to Ni3Fe |
| Earth's core | Earth's core is composed of an iron–nickel alloy[7] | about 5.5% Ni |
| Elinvar | Amanufactured alloy whose elasticity does not change with temperature; 5% Cr | 36% Ni |
| Invar | A steel manufactured to have a very low thermal expansion | 36% Ni |
| Kamacite | Anative metal found in meteoric iron | Fe[0.9]Ni[0.1] |
| Maraging steel | A strong, malleable variant of steel | 15–25% Ni |
| Meteoric iron | Anative combination of mostly kamacite and taenite, and minor amounts of tetrataenite, antitaenite, and awaruite | 5–30% Ni |
| Mu-metal | An alloy manufactured to be highly permeable to magnetism | 77% Ni |
| Planetary core | Planets, moons, and planetesimals can have cores of various iron–nickel alloys | various |
| Stainless steel | A variant of steel manufactured to be corrosion-resistant, with Cr as well as Ni | 4–8% Ni |
| Taenite | Anative metal found in meteorites | NiFe |
| Telluric iron | Anative metal found on Earth (distinct from extraterrestrial irons) | 0.05%–4% Ni |
| Tetrataenite | Anative metal found in meteorites | FeNi |
