This set of Materials Science Multiple Choice Questions & Answers (MCQs) focuses on “Thermal Processing Techniques”.
1. Which of the following is an application of cold working?
c) Hot rolling
d) Deep drawing
Explanation: In all the other option the metal is heated over the recrystallization and hence they are hot worked.
2. Which is the correct order of temperature arranged in ascending order of the following processes:
i. Partial annealing
ii. Full annealing
iii. Subcritical annealing
a) ii, i, iii
b) ii, iii, i
c) iii, ii, i
d) i, iii, ii
Explanation: Full annealing is done at a temperature higher than upper critical temperature while partial annealing is done at a temperature in between upper critical temperature and lower critical temperature and subcritical annealing is done at a temperature below lower critical temperature.
3. Which of the following can be recrystallization temperature for a pure metal? (where Tm is melting point of the metal)
Explanation: Recrystallization temperature for a pure metal is roughly in the range of 0.3 to 0.4 Tm. Only 0.3 Tm lies in that range and 0.35 Tm, 0.4 Tm and 0.45 Tm does not lie in that range.
4. What does the term soaking signify?
a) Heating to a required temperature
b) Holding at a constant temperature
c) Cooling the material
d) Heating for a long time
Explanation: Soaking is a term used in annealing in which the material is hold at a constant temperature after heating to a required temperature.
5. Which of the following will not happen when metal is cooled fast in annealing?
a) Warping of material
b) Cracking of material
c) Formation of thermo elastic stresses
d) Strength increase
Explanation: A material in annealing is cooled slowly to avoid warping of the material, cracking of the material due to the formation of thermal gradients and thermo elastic stresses inside the body.
6. In process annealing, heating is limited to avoid excessive oxidation.
Explanation: In process annealing, the material is heated to revert the effects of work hardening by recovery and recrystallization and heating is done in such a way that excessive grain growth and oxidation can be avoided.
7. Which of the following does not happen when a material is annealed?
a) Internal stresses get relieved
b) Increase in ductility
c) Decrease in toughness
d) Increase in softness
Explanation: A material is annealed to relieve internal stresses, increase ductility, toughness and softness and produce specific microstructure.
8. Which material is present above the upper critical temperature line in an iron carbon phase diagram?
Explanation: Above the upper critical line in a iron carbon phase diagram, all the material is austenite while below the lower critical no austenite material exists.
9. In stress relief annealing, the annealing temperature is relatively low.
Explanation: The above statement is true. Annealing temperatures are low in stress relief annealing so that the useful effects of cold working are not eliminated.
10. Which of the following is not a type of annealing?
c) Full annealing
Explanation: Tempering is used to increase hardness by reheating and cooling the material. It is not a type of annealing. Spherodizing and normalising are types of annealing.
Sanfoundry Global Education & Learning Series – Materials Science.
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