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A simplified section of the iron-carbon equilibrium diagram is shown - Leaving Cert Engineering - Question (b) - 2008
Question (b)
A simplified section of the iron-carbon equilibrium diagram is shown. (i) Name the regions represented at 1, 2, 3, 4 and 5. (ii) Describe the structural changes th... show full transcript
Worked Solution & Example Answer:A simplified section of the iron-carbon equilibrium diagram is shown - Leaving Cert Engineering - Question (b) - 2008
Step 1
Step 2
Describe the structural changes that occur in 0.4% carbon steel as it cooled slowly from 900°C.
Answer
At 900°C, above the upper critical temperature, the carbon is dissolved in a solid solution called austenite. This has a face-centered cubic (FCC) structure above 910°C.
As slow cooling takes place to below the lower critical temperature of 723°C, ferrite and soft pearlite (ferrite and thin layers of cementite) are formed. This makes the material as soft as possible. A body-centered cubic form exists below 910°C.