This set of Heat Treatment of Metals and Alloys Multiple Choice Questions & Answers (MCQs) focuses on “Steels – Bainitic Structures”.
1. What is the structure of the upper bainite?
a) Lamellar
b) Accicular
c) Feathery
d) Plate like
View Answer
Explanation: Upper bainite has feathery structure. Pearlite has lamellar structure. Sometimes martensite has plate like microstructure. The structure of lower bainite is accicular. Martensite has lath and plate morphologies.
2. What is the structure of the lower bainite?
a) Lamellar
b) Accicular
c) Feathery
d) Plate like
View Answer
Explanation: Lower bainite has accicular structure. Upper bainite has a feathery structure. Pearlite has lamellar structure. Sometimes martensite has plate like microstructure.
3. Which one of the following statements is correct?
a) The microstructure of upper bainite consists of lath shaped ferrite with precipitated carbides parallel to the needle axis
b) The microstructure of upper bainite consists of lath shaped ferrite with precipitated carbides perpendicular to the needle axis
c) The microstructure of upper bainite consists of ferrite plates with precipitated carbides parallel to the needle axis
d) The microstructure of upper bainite consists of ferrite plates with precipitated carbides perpendicular to the needle axis
View Answer
Explanation: The microstructure of upper bainite consists of lath shaped ferrite with precipitated carbides parallel to the needle axis. It is formed in the upper region of the temperature range.
4. Which one of the following statements is correct?
a) The microstructure of lower bainite consists of ferrite plates with precipitated carbides at an angle to the minor axis of the plate
b) The microstructure of lower bainite consists of ferrite plates with precipitated carbides at an angle to the major axis of the plate
c) The microstructure of lower bainite consists of ferrite plates with precipitated carbides parallel to the minor axis of the plate
d) The microstructure of lower bainite consists of ferrite plates with precipitated carbides parallel to the minor axis of the plate
View Answer
Explanation: The microstructure of lower bainite consists of ferrite plates with precipitated carbides at an angle to the major axis of the plate. It is formed in the lower region of the temperature range.
5. Which one of the following is correct?
a) Ferrite is an active nucleus for upper bainite but not lower bainite
b) Ferrite is an active nucleus for lower bainite but not upper bainite
c) Ferrite is an active nucleus for both upper bainite and lower bainite
d) Ferrite is an active nucleus for neither upper bainite nor lower bainite
View Answer
Explanation: Both upper bainite and lower bainite are nucleated by ferrite. Ferrite is an active nucleus for both upper bainite and lower bainite.
6. The formation of cementite results in the depletion of carbon from austenite.
a) True
b) False
View Answer
Explanation: The formation of cementite results in the depletion of carbon from austenite. This is because the formation of cementite takes place by diffusion of carbon.
7. In bainite, ferrite laths are not in contact with each other.
a) True
b) False
View Answer
Explanation: In bainite, ferrite laths are not in contact with each other. This statement is incorrect. In reality, ferrite laths are in intimate contact with each other.
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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