Composition: White iron, hypoeutectic (2,90% C; 0,30% Si; 0,29% Mn; 0,022% P)

Processing: Sand casting.

Etching: Immersion 10-30 s in 2% nital.

White irons are Fe-C alloys whose microstructure can be interpreted with the metastable F-Fe₃C phase diagram. The micrographs show dendrites of primary austenite (γ), transformed to pearlite (α + Fe₃C), and a eutectic aggregate known as ledeburite (γ + Fe₃C), where the austenite phase was also transformed to pearlite. The latter constituent, with its characteristic honeycomb morphology, is therefore defined as transformed ledeburite.

According to the level rule, this specimen should contain similar amounts of primary phase and eutectic (see diagram). At higher magnifications, it is possible to see the pearlite colonies and some iron carbide needles. There are also regions where carbides predominate in the ledeburite structure.

Fe-C diagram

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