# Manufacturing Engineering Questions & Answers – Iron Carbon Phase Diagram-1

This set of Manufacturing Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Iron Carbon Phase Diagram-1”.

1. The melting point of iron (in oC) is?
a) 768
b) 1535
c) 1410
d) 910

Explanation: Melting point of iron in degree centigrade is 1535oC.

2. Iron-Carbon phase diagram is a ___________
a) Unary phase diagram
b) Binary phase diagram
c) Tertiary phase diagram
d) Ternary phase diagram

Explanation: Binary phase diagrams are based on two component systems. Here, the two components may be mixed in an infinite number of different proportions, which indicates that composition also becomes a variable, along with pressure and temperature. Iron-carbon phase diagram, Pb-Sn diagram are the best examples of this category.

3. The temperature (in oC) of peritectic reaction in iron-carbon phase diagram is?
a) 1539
b) 1493
c) 910
d) 1175

Explanation: The invariant peritectic reaction (while cooling) in Fe-C phase diagram is given by:
L (0.53%C) + δ-ferrite (BCC, 0.09%C) $$_{\overrightarrow{1493^o C}}$$ γ (FCC, 0.17%C)

4. The temperature (in oC) of eutectic reaction in iron-carbon phase diagram is?
a) 1539
b) 1493
c) 910
d) 1150

Explanation: The invariant eutectic reaction (while cooling) in Fe-C phase diagram is given by:
L (4.3%C) $$_{\overrightarrow{1150^o C}}$$ γ (FCC, 2.11%C) + Cementite (Orthorhombic, 6.67%C)

5. The temperature (in oC) of eutectoid reaction in iron-carbon phase diagram is?
a) 1120
b) 725
c) 910
d) 820

Explanation: The invariant peritectoid reaction (while cooling) in Fe-C phase diagram is given by
γ (FCC, 0.77%C) $$_{\overrightarrow{725^o C}}$$Ferrite (BCC, 0.02%C)+ Cementite (Orthorhombic, 6.67%C).
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6. The percentage of carbon at eutectic point in Fe-C phase diagram is?
a) 2.1
b) 4.3
c) 0.83
d) 0.02

Explanation: The lowest melting alloy, the Fe-4.3% C alloy is called eutectic cast iron. This is a single-phase liquid (100%) of 4.3% carbon at the eutectic temeprature 1150oC.

7. The percentage of carbon at eutectoid point in Fe-C phase diagram is?
a) 2.1
b) 4.3
c) 0.83
d) 0.02

Explanation: During cooling, austenite of 0.77% C, at a temeprature 725oC undergoes eutectoid transformation and forms a eutectoid a mixture of ferrite and cementite, known as pearlite.

8. The percentage of carbon at peritectic point in Fe-C phase diagram is?
a) 2.1
b) 4.3
c) 0.83
d) 0.18

Explanation: Percentage of carbon at peritectic point = 0.18%. Peritectic reaction in iron-carbon phase diagram takes place at constant temperature of 1493oC.

9. Which of the following reaction does not exhibit mushy zone in Fe-C phase diagram?
a) Eutectic reaction
b) Peritectic reaction
c) Eutectoid reaction
d) Peritectoid reaction

Explanation: A mushy zone is nothing but a solid-liquid mix in a two-phase region. The alloys or reactions, which exhibits lower melting points than the two pure metals are known as eutectic alloy systems taking eutectic reaction does not exhibit mushy zone.

10. γ form of iron is?
a) Magnetic
b) Non magnetic
c) Occurs below 768oC
d) Occurs above 1410oC

Explanation: γ form of iron is known as austenite (named after ‘Sir Austin), which is an interstitial solid solution of carbon in FCC iron. Austenite is soft, ductile, tough, malleable and non-magnetic.

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