Manufacturing Processes II Mcqs

Q:

During quenching, there could be a mechanism like ______

A) vacancy diffusion B) vacancy formation
C) grain diffusion D) grain boundary distortion
 
Answer & Explanation Answer: A) vacancy diffusion

Explanation: During quenching, there could be mechanisms such as vacancies diffusing to the grain boundaries leading to PFZs (Precipitate Free Zones) that become operative.

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Q:

If the quenching medium cools the specimen at a faster rate, cracks might occur in the specimen.

A) True B) False
 
Answer & Explanation Answer: A) True

Explanation: If a quenching medium that cools faster than the required rate is used, then that can sometimes lead to defects such as warping and cracking. Therefore special care should be taken while selecting the quenching medium.

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15
Q:

If a quenching medium cools slower than the required rate, the final product will have different properties than desired.

A) True B) False
 
Answer & Explanation Answer: A) True

Explanation: If a quenching medium that cools slower than the required rate is chosen, the quench is not effective in producing the required microstructures and hence properties.

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16
Q:

The heat transfer during quenching is related to heat transfer during ______

A) annealing B) boiling
C) martempering D) hardening
 
Answer & Explanation Answer: B) boiling

Explanation: The heat transfer during quenching is very closely related to heat transfer during boiling; and, boiling is a very complicated phenomenon as far as the energy transport is considered.

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21
Q:

Quenching is generally carried out to _____

A) remove brittleness B) remove rust
C) freeze the high temperature structure D) oxidise the surface of the component for good reason
 
Answer & Explanation Answer: C) freeze the high temperature structure

Explanation: Quenching is generally carried out to freeze the high temperature structure or phase in the material; however, it is not always possible for the structure to be retained.

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19
Q:

Quenching is can also be used for _____

A) fibres B) polymers
C) metallic glasses D) plastics
 
Answer & Explanation Answer: C) metallic glasses

Explanation: Quenching can also be possible to rapidly quench molten metallic liquids to retain the liquid-like structure; such materials are commonly known as metallic glasses. Quenching is also a method used to determine hardenability of materials.

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18
Q:

An alloy quenched past the nose of the C-curve in the isothermal transformation diagram will undergo _______ transformation.

A) martensitic B) perlitic
C) austentic D) ferritic
 
Answer & Explanation Answer: A) martensitic

Explanation: The most common example of quenching is what is used in steels; an alloy quenched past the nose of the C-curve in the isothermal transformation diagram will undergo a martensitic transformation, which will lead to high hardness in the material.

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20
Q:

How many types of quenching are there?

A) 2 B) 3
C) 4 D) 5
 
Answer & Explanation Answer: B) 3

Explanation: There are many different types of quenching:
• quenching in a fine vapour or mist is known as fog quenching
• if quenching is carried out directly from some other heat treatment operation (carburizing for example), it is known as direct quenching
• if only some portions of a workpiece are quenched, it is known as selective quenching.

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