250+ TOP MCQs on Iron Carbon Phase Diagram and Answers

Manufacturing Engineering Questions & Answers for freshers on “Iron Carbon Phase Diagram”.

1. Which of the following material has the carbon varying from 2.1 to 4.3%?
a) Dead steel
b) Mild steel
c) Medium carbon steel
d) Cast iron

Answer: d
Clarification: Cast irons are the alloy of iron and carbon that contains 2.1 to 4.3% C, along with other varying amounts of silicon and manganese. This varying carbon range makes them easily castable, asking them to call cast irons.

2. Which of the following material has the carbon varying from 4.3 to 6.67%?
a) Pig iron
b) Mild steel
c) Medium carbon steel
d) Cast iron

Answer: a
Clarification: Pig iron contains a very high carbon content, usually varies from 4.3 to 6.67%. The pig iron is called so, as it resembles the shape of a reclining pig.

3. The eutectoid mixture of α+Fe₃C is known as ______________
a) Ferrite
b) Pearlite
c) Cementite
d) Austenite

Answer: b
Clarification: The eutectoid mixture of ferrite (α) and cementite (Fe₃C) as alternate lamellae is known as pearlite. Pearlite is called so, as it lustres like pearl.

4. The BCC structure of Fe-C solid solution is known as ______________
a) Ferrite
b) Cementite
c) Pearlite
d) Austenite

Answer: a
Clarification: Ferrite is an interstitial solid solution of carbon in alpha iron (BCC structure). It derives its name from Latin word “ferrum” meaning iron.

5. The FCC structure of Fe-C solid solution is known as __________
a) Ferrite
b) Cementite
c) Pearlite
d) Austenite

Answer: d
Clarification: Austenite is an interstitial solid solution of carbon in γ and has FCC structure.

6. Which of the following is soft in nature?
a) Coarse pearliite
b) Fine pearlite
c) Bainite
d) Martensite

Answer: a
Clarification: Coarse pearlite forms upon annealing which makes them to posses greater interlamellar spaced ferrite and cementite, when compared with, fine pearlite which forms upon normalizing a eutectoid steel. The more interlamellar spacing makes coarse pearlite to have soft nature.

7. Which of the following is hardest in nature?
a) Coarse pearliite
b) Fine pearlite
c) Bainite
d) Martensite

Answer: d
Clarification: Martensite is the hardest phase that can be produced by quenching a steel. Its BHN is about 700. The high rate of strain hardening and dispersion strengthening mechanisms makes the martensite hardest among steel phases. Its hardness can be varied directly with varying percentage of carbon in steel.

8. Which of the following iron carbon mixture, is the product of furnace cooling?
a) Coarse pearliite
b) Fine pearlite
c) Bainite
d) Martensite

Answer: a
Clarification: Coarse pearlite is obtained when steel is slowly cooled in a furnace atmosphere, and this complete process is termed as annealing.

9. Which of the following iron carbon mixture, is the product of water cooling?
a) Coarse pearliite
b) Fine pearlite
c) Bainite
d) Martensite

Answer: d
Clarification: The body centered tetragonal (BCT) martensite is formed upon quenching a steel. Usually the quenching mediums are water, oil and brine, etc.

10. Which of the following iron carbon mixture, is the product of air cooling?
a) Coarse pearliite
b) Fine pearlite
c) Bainite
d) Martensite

Answer: b
Clarification: Fine pearlite is obtained when steel is slowly cooled in air, and this complete process is termed as normalizing.