Materials Science Questions and Answers – Recovery, Recrystallization, and Grain Growth

«
»

This set of Tricky Materials Science Questions and Answers focuses on “Recovery, Recrystallization and Grain Growth”.

1. In which of the following processes does recovery, recrystallization, grain growth take place?
a) Surface hardening
b) Tempering
c) Strengthening
d) Annealing
View Answer

Answer: d
Explanation: In the process of annealing, the crystal goes through three stages which are called recovery, recrystallization and grain growth in order.
advertisement

2. When a material is plastically deformed at low temperature(around 25 degrees) relative to the melting temperature, which of the following change isn’t observed?
a) Change in grain shape
b) Strain hardening
c) Decrease in dislocation density
d) Increase in dislocation density
View Answer

Answer: c
Explanation: When a body is plastically deformed at low temperatures compared to its melting point, we observe micro structural changes like change in grain growth, strain hardening and increase in dislocation density.

3. At which of the following temperature can recovery occur? (where Tm is melting point)
a) 0.2Tm
b) 0.4Tm
c) 0.5Tm
d) 0.6Tm
View Answer

Answer: a
Explanation: Recovery occurs at a lower temperature than recrystallization or grain growth. Recovery takes place at the temperature below 0.3Tm.
advertisement
advertisement

4. Strain-relief crystallization takes place when deformed metals are heated.
a) True
b) False
View Answer

Answer: a
Explanation: Recovery is subdivided into two parts, strain-relief crystallization and polygonization. Strain-relief crystallization occurs when deformed metals are heated and the latter takes place under certain conditions.

5. Which of the following statements are false in strain-relief crystallization?
a) Dislocation climb
b) Decrease in the electric resistance
c) Increase in density
d) Interaction of like signed dislocation
View Answer

Answer: d
Explanation: When strain-relief crystallization takes place dislocation climb, an increase in density, and a decrease in electrical conductivity. During strain-relief crystallization interaction of unlike signed dislocation is observed.
Participate in Materials Science Certification Contest of the Month Now!
advertisement

6. By what percentage can the hardness decrease after strain-relief crystallization?
a) 12%
b) 5%
c) 8%
d) 17%
View Answer

Answer: a
Explanation: After strain-relief crystallization, the hardness and the strength of the material decrease by 10-15% from their original value. On the other hand, ductility increases by that percentage.

7. In which of the following metal polygonization rarely takes place?
a) Copper
b) Iron
c) Aluminium
d) Molybdenum
View Answer

Answer: a
Explanation: Polygonization is the process in which new grain boundaries are formed and isn’t common for all metals and observed after slight deformation. In copper and its alloy, this process rarely develops.
advertisement

8. Which of the following processes can be used to refine the grain structure?
a) Recovery
b) Recrystallization
c) Grain growth
d) Such a process does not exist.
View Answer

Answer: b
Explanation: In recrystallization new grains are formed with small nuclei and they grow until they cover the whole parent material. Therefore, the new grain structure is fine and hence the grain structure is refined.

9. Lowest temperature for recrystallization for iron is 270°C
a) True
b) False
View Answer

Answer: b
Explanation: For commercially pure iron, the lowest temperature at which recrystallization can occur is equal to 450°C. For aluminium and copper, it is equal to 100°C and 270°C respectively.
advertisement

10. Which of the following is false for grain growth?
a) The grains start growing
b) Grain growth accelerates with increase in temperature
c) Decrease in free energy
d) Increase of surface energy
View Answer

Answer: d
Explanation: The surface energy decreases during grain growth because of which free energy decreases. The grain starts growing and grain growth accelerates with increase in temperature.

Sanfoundry Global Education & Learning Series – Materials Science.

To practice Tricky questions and answers on all areas of Materials Science, here is complete set of 1000+ Multiple Choice Questions and Answers.

advertisement
advertisement
Subscribe to our Newsletters (Subject-wise). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

Youtube | Telegram | LinkedIn | Instagram | Facebook | Twitter | Pinterest
Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

Subscribe to his free Masterclasses at Youtube & technical discussions at Telegram SanfoundryClasses.