Bainite
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| Iron alloy phases |
|---|
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Austenite (γ-iron; hard) |
| Types of steel |
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Carbon steel (≤2.1% carbon; low alloy) |
| Other iron-based materials |
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Cast iron (>2.1% carbon) |
Bainite is a mostly metallic substance that exists in steel after certain heat treatments. First described by Davenport E. S. and Edgar Bain, it forms when austenite (a solution of carbon in iron) is rapidly cooled past a critical temperature of 723°C (about 1333°F).
A fine non-lamellar structure, bainite commonly consists of ferrite and cementite. It is similar in constitution to pearlite, but with the ferrite forming by a displacive mechanism similar to martensite formation, usually followed by precipitation of carbides from the supersaturated ferrite or austenite.
When formed during continuous cooling, the cooling rate to form bainite is higher than that required to form pearlite, but lower than that to form martensite, in steel of the same composition.
Bainite is generally stronger but less ductile than pearlite.
[edit] External links
- Online textbook devoted to bainite, from Cambridge University Press and the Institute of Materials
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