Mechanical Behaviour Questions and Answers – Equicohesive Temperature

This set of Mechanical Behaviour Multiple Choice Questions & Answers (MCQs) focuses on “Equicohesive Temperature”.

1. At low temperature, metals under stress deform by ________
a) Slip and twin
b) Softening
c) Rupture
d) Residual stresses
View Answer

Answer: a
Explanation: At low temperature, metals under stress deform by slip and twin. These temperatures are about one half of the absolute melting temperature.

2. The fracture through grains is known as ________
a) Rupture
b) Trans granular
c) Inter crystalline
d) Intergranular
View Answer

Answer: b
Explanation: If applied stress is sufficiently large, fracture occurs through grains. It is known as trans granular fracture.

3. A fracture through grain boundaries is _________
a) Trans granular
b) Trans crystalline
c) Cohesive
d) Intergranular
View Answer

Answer: d
Explanation: On higher temperatures, grain boundaries become weak. Now crack propagate through grain boundaries. This is an intergranular fracture.
advertisement
advertisement

4. At _________________ the grain boundaries of polycrystalline metals act as ________ for cracks.
a) Low temperature, barrier
b) High temperature, barrier
c) High stress, barrier
d) High stress, nucleation sites
View Answer

Answer: a
Explanation: At lower temperatures, the grain boundaries of polycrystalline materials are stronger than grains and it acts as a barrier for dislocation movement.

5. Which temperature is more important for alloys?
a) Melting temperature
b) Boiling temperature
c) Recrystallization temperature
d) Sub-zero temperature
View Answer

Answer: c
Explanation: Recrystallization temperature is more important than melting temperature. It decides the phase transformation.

6. Why grain boundaries become weak on high temperatures?
a) Mobility of atoms
b) Partial melting
c) Dislocation pile up
d) Substructure
View Answer

Answer: a
Explanation: The mobility of atoms in the grain boundary regions becomes high. Grains still maintain their stability. Hence grain boundaries are weaker.

7. With an increase in temperature, the cohesiveness of grain boundary ________
a) Increases
b) Decreases
c) Remains constant
d) First increases, then decrease
View Answer

Answer: b
Explanation: On higher temperature, atoms become more mobile. The cohesiveness of the grain boundary decreases.
advertisement

8. Grain boundary ________ occurs at a high temperature causing an intergranular fracture.
a) Gliding
b) Strengthening
c) Sliding
d) Twinning
View Answer

Answer: c
Explanation: At high temperatures, atomic mobility increases in grain boundaries. It causes grain boundary sliding causing an intergranular fracture.

9. Which of the following temperature is used to differentiate transgranular and intergranular modes of fracture?
a) Recrystallization
b) Equi-cohesive
c) Curie
d) Critical
View Answer

Answer: b
Explanation: Equicohesive temperature is the temperature at which the strength of grain and grain boundary is the same. It is used to differentiate the mode of fracture, which has transgranular fracture below equicohesive temperature and intergranular fracture at above equicohesive temperature.
advertisement

10. With increasing strain rate, ECT _________
a) Increases
b) Decreases
c) Remains constant
d) First increases, then decrease
View Answer

Answer: a
Explanation: On decreasing strain rate, ECT lowers. Hence the tendency for intercrystalline fracture increases.

11. Which process doesn’t occur at high temperature?
a) Sub grain formation
b) Recovery
c) Recrystallization
d) Slip and twinning
View Answer

Answer: d
Explanation: At low temperatures, metals under stress deform principally by slip or twinning. Sub grain formation recovery and recrystallization occur at high temperature.

12. Equicohesive temperature is twice that of recrystallization.
a) True
b) False
View Answer

Answer: b
Explanation: For most of the metals, the equicohesive temperature is equal to recrystallization temperature. Recrystallization temperature is fixed while equicohesive temperature has a range.

13. Below the equicohesive temperature, the strength of grain boundaries are higher than grains.
a) True
b) False
View Answer

Answer: a
Explanation: At equicohesive temperature, the strength of grains and grain boundary is equal. Below the equicohesive temperature, grain boundaries are stronger than grains.

Sanfoundry Global Education & Learning Series – Mechanical Behaviour & Testing of Materials.

To practice all areas of Mechanical Behaviour & Testing of Materials, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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 & discussions at Telegram SanfoundryClasses.