This set of Heat Treatment of Metals and Alloys Multiple Choice Questions & Answers (MCQs) focuses on “Phase Diagrams and Effect of Alloying Elements on Fe-Fe3C Phase Diagram”.
1. Which one of the following is a eutectic reaction?
a) Liquid + Delta-carbide → Austenite
b) Liquid → Austenite + Fe3C
c) Austenite → Ferrite + Fe3C
d) Ferrite + Delta-carbide → Austenite
View Answer
Explanation: Liquid + Delta-carbide → Austenite is a pearlitic reaction. Austenite → Ferrite + Fe3C is a eutectoid reaction. Ferrite + Delta-carbide → Austenite is a peritectoid reaction.
2. Which of the following is the softest structure in Fe-Fe3C diagram?
a) Alpha-ferrite
b) Cementite
c) Pearlite
d) Austenite
View Answer
Explanation: Cementite is the hardest structure that appears on the Fe-Fe3C diagram. Pearlite is a very fine plate like or lamellar mixture of ferrite and cementite. Austenite is soft, ductile tough and malleable but harder than ferrite.
3. At what temperature does the pearlitic reaction takes place in Fe-Fe3C diagram.
a) 1147°C
b) 910°C
c) 1495°C
d) 723°C
View Answer
Explanation: Eutectic reaction takes place at 1147°C. At 723°C, eutectoid reaction takes place. At 1495°C, peritectic reaction takes place. At exactly 910°C, no transformation takes place because of 0% carbon content, ferrite will remain ferrite.
4. Which one of the following elements is an austenite stabilizer?
a) Cobalt
b) Molybdenum
c) Tungsten
d) Chromium
View Answer
Explanation: Cobalt is an austenite stabilizer. Molybdenum, Tungsten, and Chromium are ferrite stabilizers.
5. Which of the phases have FCC structure?
a) Ferrite
b) Austenite
c) Epsilon carbide
d) Martensite
View Answer
Explanation: Ferrite has BCC structure; epsilon carbide has HCP structure and martensite has BCT structure. Only Austenite has an FCC structure.
6. Which one of the following elements decreases the stability of austenite?
a) Copper
b) Zinc
c) Chromium
d) Nickel
View Answer
Explanation: Austenite stabilizers increase the stability of austenite while ferrite stabilizers decrease the stability of austenite. Copper, Zinc and Nickel are austenite stabilizers so they increase the stability of austenite. On the other hand, Chromium is a ferrite stabilizer so it decreases the stability of austenite.
7. Which one of the following elements neither forms graphite nor carbide?
a) Iron
b) Manganese
c) Cobalt
d) Silicon
View Answer
Explanation: Iron is a carbide forming element. Manganese is also a carbide forming element. Silicon is a graphite forming element. Cobalt is a neutral element. It does not form graphite or carbide.
8. Which of the following elements decreases the eutectoid temperature?
a) Chromium
b) Nickel
c) Silicon
d) Molybdenum
View Answer
Explanation: Austenite stabilizers decrease the eutectoid temperature while ferrite stabilizers increase the eutectoid temperature. Among the options given Nickel is an austenite stabilizer while others are ferrite stabilizers.
9. Which one of the following ferrite stabilizers does not have BCC structure?
a) Silicon
b) Molybdenum
c) Titanium
d) Chromium
View Answer
Explanation: Molybdenum, Titanium and Chromium have BCC structure like most of the ferrite stabilizers. Silicon is a special case which being a ferrite stabilizer have a diamond cubic structure.
10. Which of the following elements is most effective in increasing the eutectoid temperature?
a) Molybdenum
b) Titanium
c) Tungsten
d) Silicon
View Answer
Explanation: Effect of alloying elements on the increase in eutectoid temperature follows the order
+ Titanium > Molybdenum > Silicon > Tungsten.
Sanfoundry Global Education & Learning Series – Heat Treatment of Metals and Alloys.
To practice all areas of Heat Treatment of Metals and Alloys, here is complete set of Multiple Choice Questions and Answers.
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