Pearlite

For the amorphous volcanic glass, see perlite.
Steels
Phases
Microstructures
Classes
Other iron-based materials
SEM micrograph of etched pearlite, 2000X.
Atom probe tomography of pearlite. The red dots indicate the positions of carbon atoms. Iron atoms are not shown. The nanotube is shown for size reference.
Pearlite occurs at the eutectoid of the iron-carbon phase diagram (near the lower left).

Pearlite is a two-phased, lamellar (or layered) structure composed of alternating layers of ferrite (87.5 wt%) and cementite (12.5 wt%) that occurs in some steels and cast irons. During slow cooling of an iron-carbon alloy, pearlite forms by a eutectoid reaction as austenite cools below 723 °C (1,333 °F) (the eutectoid temperature). Pearlite is a microstructure occurring in many common grades of steels.