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.
c) ϒ’ solvus
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.
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.
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
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.
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
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
d) Strain rate
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
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
d) Second phase particles
Explanation: Second phase particles are athermal obstacles. Other three options are thermal obstacles.
10. P-N stress is the ___________ obstacle.
b) Long range
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.
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.
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.
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.