250+ TOP MCQs on Iron Carbon Phase Diagram and Answers

Manufacturing Engineering Multiple Choice Questions on “Iron Carbon Phase Diagram-1”.

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

Answer: b
Clarification: Melting point of iron in degree centigrade is 1535^oC.

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

Answer: b
Clarification: 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

Answer: b
Clarification: 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

Answer: d
Clarification: 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

Answer: b
Clarification: 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).

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

Answer: b
Clarification: 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 1150^oC.

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

Answer: c
Clarification: During cooling, austenite of 0.77% C, at a temeprature 725^oC 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

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

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

Answer: a
Clarification: 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 768^oC
d) Occurs above 1410^oC

Answer: a
Clarification: 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.