PART III: Multiple-Answer Questions, which have more than one correct answer (2
ID: 1730301 • Letter: P
Question
PART III: Multiple-Answer Questions, which have more than one correct answer (2 points each and 20 points in total)
1. Binding energy of chemical bonds decides materials’ strength, elastic modulus, melting point, coefficient of thermal expansion, etc. Because covalent bonding is characteristic of high binding energy, covalent materials generally have:
High strength.
High elastic modulus.
High melting points.
High coefficient of thermal expansion.
The correct answers are: .
2. Chemical bonds play crucial roles at determining materials strength and stability. Primary chemical bonds include:
Metallic bond
Ionic bond
Covalent bond
Hydrogen bond
Van der Waals bond
The correct answers are: .
3. When dislocation density increases, metallic materials have:
Higher strength.
Lower strength.
Higher ductility.
Lower ductility.
The correct answers are: .
4. When grain size deceases, metallic materials have, as compared to coarse-grain counterparts:
Higher strength.
Lower strength.
Higher ductility.
Lower ductility.
The correct answers are: .
5. Forming an oversaturated solid solution is the first step for aging treatment as well as other precipitation treatments. An oversaturated solid solution is characteristic of:
Oversaturated vacancies.
Oversaturated alloying atoms.
Oversaturated dislocations.
Oversaturated crystal grains.
The correct answers are: .
6. Cold work means mechanically deforming a metal at relatively low temperatures. The microstructure of a cold-worked metal is characteristic of:
High-density point defects.
High-density dislocations.
Residual stress.
Deformation texture.
Sub-grains
The correct answers are: .
7. Al alloys can be divided into non-heat-treatable and heat-treatable alloys. Non-heat-treatable Al alloys can be strengthened by:
Precipitation strengthening (or age-hardening).
Solid-solution (or substitutional atom) strengthening.
Cold work (or dislocation or strain) strengthening.
Fine-grain strengthening.
The correct answers are: .
8. Thermosetting polymers are in general characteristic of:
High strength
Low strength
High ductility
Low ductility
Softening and gradually melting with increasing temperature
Not softening and not gradually melting with increasing temperature until decomposing.
The correct answers are: .
9. A hypoeutectoidic steel alloy is equilibrium solidified (as shown in the figure), the microstructure obtained includes:
Austenite.
Ferrite.
Fe3C.
Pearlite.
The correct answers are: .
10. For cast irons, one of the main purposes of adding alloying elements and performing heat treatment is to obtain spherical graphite particles instead of Fe3C particles. This is because:
Spherical graphite particles can efficiently increase the strength of cast irons
Spherical graphite particles can efficiently increase the ductility of cast irons
Spherical particles can efficiently increase the toughness of cast irons
Spherical particles can efficiently increase the machinability of cast irons
Spherical particles can efficiently increase the damping properties of cast irons
The correct answers are: .
Explanation / Answer
High strength and High melting points.
Metallic bond
Ionic bond
Covalent bond
Hydrogen bond
Higher strength.
4. When grain size deceases, metallic materials have, as compared to coarse-grain counterparts:
Higher strength.
High-density dislocations
Precipitation strengthening (or age-hardening).
8. Thermosetting polymers are in general characteristic of:
High strength
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