This set of Heat Treatment of Metals and Alloys Multiple Choice Questions & Answers (MCQs) focuses on “Steels – Athermal and Isothermal Martensitic”.
1. What is the maximum temperature at which martensite can be formed by plastic deformation?
a) Ms
b) Mf
c) Greater than Ms
d) Between Ms and Mf
View Answer
Explanation: The maximum temperature at which martensite can be formed by plastic deformation is given by Md. This temperature is greater than Ms Temperature.
2. During Athermal martensite transformation, what is the speed of growth of nuclei?
a) Speed of light
b) Speed of sound
c) Very slow speed
d) Speed of normalizing
View Answer
Explanation: During Athermal martensite transformation, nuclei formed grow at the speed of sound. This is the characteristic feature of this transformation.
3. Which one of the following statements is correct?
a) In lath martensite, martensite is present in strip form
b) In lath martensite, martensite is present in lens type form
c) In plate martensite, martensite is present in strip form
d) In lath martensite, martensite is present in plate form
View Answer
Explanation: In lath martensite, martensite is present in strip form. The maximum length of strip is limited to the distance between grain boundaries of austenitic grain.
4. What is the thickness of strip formed in lath martensite?
a) .05 μm – 0.08 μm
b) 0.1 μm – 0.2 μm
c) 0.5 μm – 1 μm
d) 2 μm – 5 μm
View Answer
Explanation: In lath martensite, martensite is present in the form of strips. The thickness of strip usually lies between 0.1 μm – 0.2 μm. It cannot be 2 μm – 5 μm as martensite will lose its brittleness and hardness.
5. Which one of the following is the characteristic feature of lath?
a) High dislocation density and high angle grain boundaries
b) High dislocation density and low angle grain boundaries
c) Low dislocation density and high angle grain boundaries
d) Low dislocation density and low angle grain boundaries
View Answer
Explanation: High dislocation density and low angle grain boundaries are the characteristic features of lath. Several small packets of lath are present within the grain boundaries.
6. Lath martensite is generally found in which category of steels?
a) High carbon steels
b) Low and medium carbon steels
c) High and medium carbon steels
d) Low and high carbon steels
View Answer
Explanation: Lath martensite is usually formed in low and medium carbon steels. They are also formed in low and medium carbon grades of low alloy steels.
7. Plate martensite is formed in which category of steels?
a) High carbon steels
b) Low and medium carbon steels
c) High and medium carbon steels
d) Low and high carbon steels
View Answer
Explanation: Plate martensite is formed in high carbon steels. They are also formed in high alloy steels. Lath martensite is formed in low and medium carbon steels.
8. Plate martensite is popularly known as lenticular martensite.
a) True
b) False
View Answer
Explanation: Plate martensite is popularly known as lenticular martensite. This statement is correct. The reason behind this is that it has a lens type shape.
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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