Austenite

A high-temperature phase of iron, stable above 911ºC.

Austenite has a face-centred cubic crystal structure and is commonly denoted both in writings and on phase diagrams by the use of the Greek letter gamma (γ).
Austenite is a very soft, non-magnetic form of iron.

It is the ability of austenite to absorb just over 2% carbon that makes the carburising and carbonitriding processes possible. The addition of carbon makes austenite stable at temperatures as low as 723ºC. However, if significant quantities of chromium and nickel are added, the austenite becomes stable at room temperature. These steels are the well-known austenitic stainless steels containing 18% chromium and 8% or 10% nickel.

Austenite was named after the British metallurgist, Sir William Chandler Roberts-Austen (1843-1902). Roberts-Austen published the first iron-carbon phase diagram.

See also austenitic, retained austenite.