Austenite, also known as gamma phase iron, is a metallic non-magnetic allotrope of iron

Allotropes of iron

Iron represents perhaps the best-known example for allotropy in a metal. At atmospheric pressure, there are three allotropic forms of iron, known as α, γ and δ. At high pressure, a fourth form exists, called ε...

 or a solid solution

Solid solution

A solid solution is a solid-state solution of one or more solutes in a solvent. Such a mixture is considered a solution rather than a compound when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the mixture remains in a single homogeneous phase...

 of iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

, with an alloy

Alloy

An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...

ing element. In plain-carbon steel

Plain-carbon steel

Carbon steel, also called plain-carbon steel, is steel where the main interstitial alloying constituent is carbon. The American Iron and Steel Institute defines carbon steel as: "Steel is considered to be carbon steel when no minimum content is specified or required for chromium, cobalt,...

, austenite exists above the critical eutectoid temperature of 1000 K (1,340.3 °F); other alloys of steel

Steel

Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 have different eutectoid temperatures. It is named after Sir William Chandler Roberts-Austen

William Chandler Roberts-Austen

Sir William Chandler Roberts-Austen, , was a metallurgist noted for his research on the physical properties of metals and their alloys. Austenite is named in his honor....

 (1843–1902).
From 912 to 1394 °C (1,673.6 to 2,541.2 F) alpha iron undergoes a phase transition

Phase transition

A phase transition is the transformation of a thermodynamic system from one phase or state of matter to another.A phase of a thermodynamic system and the states of matter have uniform physical properties....

 from body-centred cubic (BCC) to the face-centred cubic (FCC) configuration of gamma iron, also called austenite.