Which phase of steel has a face-centered cubic structure?

The phase of steel that has a face-centered cubic (FCC) structure is austenite. In metallurgy, austenite is the phase that occurs when iron is heated to a temperature where it becomes non-magnetic and can dissolve a significant amount of carbon, typically between 2 to 4% at high temperatures. This FCC structure of austenite allows for a unique combination of ductility and strength, making it an important phase in various heat treatment processes for steels.

Austenite is notably stable at elevated temperatures and can transform into other microstructures such as ferrite and cementite upon cooling, depending on the cooling rate and the composition of the steel. This transformation and the ability to manipulate the microstructure of steel is crucial for designing materials with desired mechanical properties.

The other phases mentioned, such as pyrite and cementite, do not exhibit a face-centered cubic structure. Pyrite is an iron sulfide mineral with a crystalline structure differing from metals, while cementite (iron carbide) has a different orthorhombic crystal structure. Therefore, austenite is distinctively identified by its FCC structure, which underpins its significant role in steel metallurgy.