This set of Materials Science Multiple Choice Questions & Answers (MCQs) focuses on “Strengthening Mechanisms”.
1. Which of the following isn’t a strengthening mechanism?
a) Grain size reduction
b) Solid solution strengthening
c) Strain hardening
d) Grain size increment
Explanation: Grain size reduction, solid solution strengthening and strain hardening are all strengthening mechanisms which increase the hardness of the material. Grain size increment isn’t a strengthening mechanism.
2. Which of the following isn’t a strengthening mechanism for multi-phase materials?
a) Precipitation strengthening
b) Dispersion strengthening
c) Solid solution strengthening
d) Martensite strengthening
Explanation: Precipitation strengthening, dispersion strengthening, martensite strengthening are strengthening mechanism used for multi-phase materials. Solid solution strengthening is used for single-phase materials.
3. The yield strength of a material going through grain size reduction increases by a factor, k multiplied by:(where d is the diameter of grain)
Explanation: Yield strength relation is given by Hall-Petch relation in which final yield strength is equal to initial yield strength plus k( a constant) multiplied by d-1/2.
4. Which of the following is not improved by grain size reduction?
Explanation: Grain size reduction increases the hardness, toughness and the strength of the material. Elasticity is not increased by grain size reduction.
5. Which of the following is not a way of interaction between solute atoms and dislocation?
a) Elastic interaction
b) Plastic interaction
c) Modulus interaction
d) stacking fault interaction
Explanation: Plastic interaction isn’t a way of interaction of solute atom and dislocation while plastic interaction, modulus interaction and stacking fault interaction are ways of an interaction of solute atoms and dislocation.
6. Which of the following interactions will continue to act to about 0.6Tm?(Where Tm is melting point)
a) Elastic interaction
b) Modulus interaction
c) Electrical interaction
d) Long range interaction
Explanation: Elastic interaction, modulus interaction, long range interaction are all long range interactions which act at 0.6 Tm while short range interaction like electrical interaction doesn’t act at 0.6Tm.
7. Which is not a correct term for bands in yield point phenomenon?
a) Lüders bands
b) Hartmann lines
c) stretcher stains
d) Lüders lines
Explanation: Lüders lines isn’t a correct term for bands in yield point phenomenon. While Lüders bands, Hartmann lines, stretcher stains are a correct term which can be used for bands in yield point phenomenon.
8. At what angle are Hartmann lines inclined to the tensile axis?
a) 45 degrees
b) 15 degrees
c) 30 degrees
d) 20 degrees
Explanation: The Hartmann lines are inclined to an angle of 45 degrees approximately to the tensile axis.
9. In strain hardening, the body is plastically deformed.
Explanation: Strain hardening is a process which is done on a ductile method by deforming them plastically and increasing strain in the body and hence increasing the hardness.
10. In strain hardening, there is an increase in density.
Explanation: In strain hardening apart from changes in mechanical properties there are physical changes like decrease in density, a small increase in the thermal coefficient of expansion.
Sanfoundry Global Education & Learning Series – Materials Science.
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