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| Phase Diagrams | ||||||||||||
| ·
The
Eutectoid
and Peritectoid
invariant reactions occur for systems
in which all of the phases involved are solids.
· The Eutectoid reaction involves a single solid phase decomposing into two different solid phases: γ → α + β. The iron-carbon system shows this type of reaction. · The Peritectoid invariant reaction involves two solids reacting to form a single solid phase: γ → α + β. Reactions of this type are found in the copper-zinc (brass) binary system. · Because solid state diffusion is involved in the phase change reactions, these processes are slower than those in which a liquid phase is present. Cooling rates must be reduced to approximate a quasi-static thermodynamic process. |
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