pearlite

Pearlite is a microstructure found in iron-carbon alloys, primarily steel and cast iron, that have been slowly cooled. It is a lamellar mixture composed of alternating plates of ferrite (iron) and cementite (iron carbide, Fe₃C). This structure forms when austenite, a high-temperature phase of iron, transforms during cooling.12

The presence and amount of pearlite significantly influence the properties of steel. Steel with a higher carbon content (around 0.77%) will consist of approximately 50% pearlite and 50% ferrite, resulting in a harder material than pure iron. Steels with more than 0.77% carbon will also contain cementite in addition to pearlite, making them even harder. The name "pearlite" comes from its resemblance to pearls.21