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1. What is Peritectic reaction at 1495°C?
a) L (0.53% C) + δ(0.09% C) → γ(0.17% C)
b) L (4.3% C) → γ(2.1 % C) + Fe3C (6.67% C)
c) γ (0.8 % C) → α (0.025% C) + Fe3C (6.67% C)
d) L (0.53% C) + δ(0.09% C) → γ (0.8 % C)

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Answer: a [Reason:] Peritectic reaction at 1495°C is L (0.53% C) + δ(0.09% C) → γ(0.17% C).

2. What is Eutectic reaction at 1146°C?
a) L (0.53% C) + δ(0.09% C) → γ(0.17% C)
b) L (4.3% C) → γ(2.1 % C) + Fe3C (6.67% C)
c) γ (0.8 % C) → α (0.025% C) + Fe3C (6.67% C)
d) L (0.53% C) + δ(0.09% C) → γ (0.8 % C)

View Answer

Answer: b [Reason:] Eutectic reaction at 1146°C is L (4.3% C) → γ(2.1 % C) + Fe3C (6.67% C).

3. What is Eutectoid reaction at 727°C?
a) L (0.53% C) + δ(0.09% C) → γ(0.17% C)
b) L (4.3% C) → γ(2.1 % C) + Fe3C (6.67% C)
c) γ (0.8 % C) → α (0.025% C) + Fe3C (6.67% C)
d) L (0.53% C) + δ(0.09% C) → γ (0.8 % C)

View Answer

Answer: c [Reason:] Eutectoid reaction at 727°C is γ (0.8 % C) → α (0.025% C) + Fe3C (6.67% C).

4. The eutectic mixture of austenite (γ) and cementite (Fe3C) is called __________
a) Ledeburite
b) Pearlite
c) Hyper and hypoeutectoid steel
d) Cast iron

View Answer

Answer: a [Reason:] Eutectic reaction at 1146°C is L (4.3% C) → γ(2.1 % C) + Fe3C (6.67% C). The eutectic mixture of austenite (γ) and cementite (Fe3C) is called Ledeburite.

5. The eutectoid mixture of ferrite (α) and cementite (Fe3C) is called __________
a) Ledeburite
b) Pearlite
c) Hyper and hypoeutectoid steel
d) Cast iron

View Answer

Answer: b [Reason:] The pearlite is formed under equilibrium Conditions which consists of alternate lamellas or layers of ferrite and Fe3C.

6. Compositions right and left of 0.8% C of Pearlite are called __________
a) Ledeburite
b) Ferrite
c) Hyper and Hypoeutectoid steel
d) Cast iron

View Answer

Answer: c [Reason:] Hypoeutectoid steels – α+ p; hypereutectoid – Fe3C + p.

7.Compositions above 2.1% C is called as _______
a) Ledeburite
b) Ferrite
c) Hyper and Hypoeutectoid steel
d) Cast iron

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Answer: d [Reason:] Compositions up to 2.1% of Carbon are considered steels and beyond this it is considered as cast iron.

8. From the following figure if Diffusion rates below Ms is so low that γ → M transformation is a diffusionless process then what is change in crystal structure
materials-science-questions-answers-online-quiz-q8
a) FCC → BCT
b) FCC → BCC
c) BCC → BCT
d) BCT → BCC

View Answer

Answer: a [Reason:] Diffusion rates below Ms is so low that γ → M transformationis a diffusion less process (the C content remains same). However, the crystal structure changes from FCC (γ) to body centered tetragonal (BCT).

9.Finer size pearlite is called _______
a) Troostite
b) Ledeburite
c) Ferrite
d) Sorbite

View Answer

Answer: d [Reason:] Finer size pearlite is called sorbiteand very fine size pearlite is called troostite.

10. A eutectoid steel is slowly cooled from temperature of 750°C to atemperature just below 727°C. Calculate the percentage of ferrite and cementite.
a) 88.3% and 11.7%
b) 70% and 30 %
c) 85.4% and 14.6%
d) 20% and 20%

View Answer

Answer: a [Reason:] Eutectoid composition – 0.8% of Carbon, Ferrite composition- 0.025% of Carbon and cementite – 6.67% C. Apply the lever rule to get the percentages as % of Ferrite = 100(6.67 – 0.80)/(6.67 – 0.025)=88.3% ferrite %of Cementite = 100(0.80 – 0.025)/(6.67 – 0.025) =11.7%.

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