This set of Mechanical Behaviour Multiple Choice Questions & Answers (MCQs) focuses on “Mechanism of Creep Deformation”.
1. Co is added in Ni-base alloy so as to increase ___________ temperature.
a) Melting
b) Boiling
c) ϒ’ solvus
d) Recrystallization
View Answer
Explanation: Co is added in Ni-base alloy so as to increase ϒ’ solvus temperature. It hence improves temperature capability.
2. ___________ impart hot corrosion resistance in Ni-base superalloys.
a) Cr
b) Ti
c) Mo
d) Ta
View Answer
Explanation: Cr and Ti are effective in imparting hot corrosion resistance. Cr, Mo and Ta form carbides.
3. _________ provides oxidation resistance in Ni-base superalloys.
a) Mo
b) Ta
c) Al
d) W
View Answer
Explanation: Al and Cr provide oxidation resistance in Ni-base superalloys. Cr, Mo and Ta form carbides.
4. Co-base superalloys can sustain temperature ___________
a) 500-600 °C
b) 600-740 °C
c) 700-1040 °C
d) 1000-2040 °C
View Answer
Explanation: Co-base superalloys can sustain temperature 700-1040 °C. These are on stresses 35 to 70 MPa.
5. P-N stress is low for ___________ structure.
a) FCC
b) BCC
c) BCT
d) SC
View Answer
Explanation: P-N stress is low for FCC and HCP structure. It is because of slip planes.
6. ___________ dominates at all temperatures but above the normalized stress of 10-2.
a) Coble creep
b) Nabarro-Herring creep
c) Dislocation creep
d) Dislocation glide
View Answer
Explanation: Dislocation glide dominates at all temperatures but above the normalized stress of 10-2. The applied stress is higher for dislocation glide than for creep deformation.
7. Normalized stress is the ratio of applied stress and ___________
a) Bulk modulus
b) Shear modulus
c) Strain
d) Strain rate
View Answer
Explanation: Normalized stress is the ratio of applied stress and shear modulus. It is dimensionless. It is denoted as σ/G.
8. Which of the following is a thermal obstacle?
a) Dislocation on parallel slip planes
b) Incoherent precipitate
c) Climb of edge dislocations
d) Second phase particles
View Answer
Explanation: Climb of edge dislocations is a thermal obstacle. Other three options are athermal obstacles.
9. Which of the following is an athermal obstacle?
a) Forest dislocations
b) Cross slip
c) Climb
d) Second phase particles
View Answer
Explanation: Second phase particles are athermal obstacles. Other three options are thermal obstacles.
10. P-N stress is the ___________ obstacle.
a) Athermal
b) Long range
c) Thermal
d) Kinetic
View Answer
Explanation: P-N stress is the thermal obstacle. This is also known as a short-range obstacle. These are responsible for the dynamic aspect of plastic deformation.
11. When dislocation glide is assisted by vacancy diffusion, resulting creep is known as ___________ creep.
a) Coble
b) Dislocation
c) Diffusion
d) Nabarro-Herring
View Answer
Explanation: When dislocation glide is assisted by vacancy diffusion, resulting creep is known as dislocation creep. It is similar to a screw dislocation containing a jog which is an edge in orientation.
12. In ultra-fine grain polycrystalline metal, grain boundary sliding is predominant.
a) True
b) False
View Answer
Explanation: In single crystal grain boundary sliding is negligible. While in ultrafine polycrystalline metal, grain boundary sliding predominant.
13. Motion of jogs is the athermal obstacle.
a) True
b) False
View Answer
Explanation: Motion of jogs in screw dislocation is the thermal activated process. It is a thermal obstacle.
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.
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