ledeburiet

Ledeburite is a microstructural constituent observed in iron–carbon alloys with high carbon content. It denotes the eutectic mixture of austenite (gamma-iron) and cementite (Fe3C) that forms at the eutectic composition of about 4.3 weight percent carbon and a temperature near 1147°C.

During solidification, the liquid transforms by a eutectic reaction into austenite and cementite: L -> gamma + Fe3C. The result is a characteristic network or lamellar intergrowth of cementite within the austenitic matrix. The morphology can appear as coarse lamellae or rosettes, depending on cooling conditions and alloy composition.

As cooling continues below the eutectic temperature, the austenite portion may transform into other microstructures such as pearlite or bainite, depending on cooling rate and alloying elements, while the cementite phases persist. In some heat treatments, ledeburite may decompose further, influencing hardness, brittleness, and machinability.

Occurrence and significance: Ledeburite is typically observed in high-carbon cast irons and steels near the eutectic composition. It is a term used in metallurgy to describe a specific solidification microstructure rather than a mineral. Its presence helps explain certain mechanical properties and the solidification paths of iron–carbon alloys, especially those with carbon contents around 4 wt% or higher.