GATE MT 2012 Q39. Match the phases of steel in Group I with the crystal structures in Group II
GATE MT 2012 Q39. Match the phases of steel in Group I with the crystal structures in Group II
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Correct answer is option C. Martensite forms during quenching, when the face centred cubic lattice of austenite is distorted into the body centred tetragonal structure without the loss of its contained carbon atoms into cementite and ferrite. Cementite (or iron carbide) is a compound of iron and caRead more
Correct answer is option C.
- Martensite forms during quenching, when the face centred cubic lattice of austenite is distorted into the body centred tetragonal structure without the loss of its contained carbon atoms into cementite and ferrite.
- Cementite (or iron carbide) is a compound of iron and carbon, more precisely an intermediate transition metal carbide with the formula Fe3C. By weight, it is 6.67% carbon and 93.3% iron. It has an orthorhombic crystal structure.
- Austenite has a cubic-close packed crystal structure, also referred to as a face-centred cubic structure with an atom at each corner and in the centre of each face of the unit cell. Ferrite has a body-centred cubic crystal structure and cementite has an orthorhombic unit cell containing four formula units of Fe3C.
- Ferrite is a body-centred cubic (BCC) form of iron, in which a very small amount (a maximum of 0.02% at 1333°F / 723°C) of carbon is dissolved.
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