This set of Heat Treatment of Metals and Alloys Multiple Choice Questions & Answers (MCQs) focuses on “Steels – Mechanism of Bainitic Transformation”.
1. Bainite transformation is a diffusion controlled process.
a) True
b) False
View Answer
Explanation: Bainite transformation is diffusion controlled process. The presence of the incubation period is a proof of that.
2. Which one of the following statements is correct?
a) Only diffusion processes are involved in bainite formation
b) Only diffusionless processes are involved in bainite formation
c) Only shear processes are involved in bainite formation
d) Both diffusion and diffusionless processes are involved in it
View Answer
Explanation: Bainite is a diffusion controlled process. But the temperature at which bainite is formed is very low, therefore diffusion is very slow. That is why diffusionless processes are also involved in it.
3. Which one of the following statements is correct?
a) Ms temperature is greater than Bs temperature
b) Ms temperature is lower than Bf temperature
c) Ms temperature lies between Bs and Bf temperature
d) Mf temperature is greater than Bs temperature
View Answer
Explanation: The Ms temperature for low carbon content austenitic regions lie between Bs and Bf temperature. This is the point where the shear process takes place.
4. Which one of the following statements is correct?
a) Bainitic transformation is never completed
b) Bainitic transformation is always completed
c) Bainitic transformation is completed by diffusion process alone
d) Bainitic transformation is completed by diffusionless process alone
View Answer
Explanation: Bainitic transformation is never completed. The reason is that when the bainitic transformation takes place, some of the austenite also gets partially transformed to martensite by diffusionless process.
5. Which one of the following is not the final product of bainitic transformation?
a) Bainite and martensite
b) Bainite and retained austenite
c) Austenite and ferrite
d) Bainite and retained austenite or bainite and martensite
View Answer
Explanation: Bainite and retained austenite or bainite and martensite are the final product of bainitic transformation. The reason is the partial transformation of austenite to martensite.
6. Which one of the following statements is correct?
a) Degree of super saturation of ferrite with carbon increases with increasing temperature
b) Degree of super saturation of ferrite with carbon decreases with increasing temperature
c) Degree of super saturation of ferrite with carbon remains constant with increasing temperature
d) Ferrite is not supersaturated with carbon
View Answer
Explanation: Ferrite has very low solubility for carbon. That is why it gets supersaturated with carbon during transformation. This degree of super saturation of ferrite with carbon decreases with increasing transformation temperature.
7. Carbon may precipitate out of supersaturated ferrite.
a) True
b) False
View Answer
Explanation: Carbon may precipitate out of supersaturated ferrite. This happens when bainitic transformation proceeds at a lower region of transformation temperature.
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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