Ledeburit
Ledeburit describes certain eutectic structures of the iron-carbon alloys . It was named after its discoverer, the metallurgist Karl Heinrich Adolf Ledebur (1837–1906).
Ledeburite occurs with carbon contents between 2.06% and 6.67% (line ECF in the iron-carbon diagram ). The carbon content of the eutectic mixture is 4.3%, the melting temperature is 1147 ° C (eutectic point C). At this carbon concentration, 100% ledeburite is present in the structure.
Ledeburite is not a phase , it is a phase mixture consisting of (disintegrated) austenite and cementite . A distinction is made between Ledeburit I and Ledeburit II: While Ledeburit I (just below 1147 ° C) is a structure of austenite and cementite, Ledeburit II (room temperature) consists of cementite with secondary cementite that has crystallized on (from the austenite when the temperature drops Temperature) and (with slow cooling) of perlite . The pearlite is formed by the eutectoid decay of the austenite from the ledeburite I at 723 ° C. In the case of more rapid cooling, bainite can also be present instead of pearlite or, in the case of very rapid cooling, martensite .
- Ledeburite I: austenite + Fe 3 C
- Ledeburite II: pearlite + Fe 3 C