MAE201: Materials Science, Summer 2022
Mid-Exam
June 05, 2022,
11:45AM-2:25PM
Ch. 1~8
Open-book, Open-notes
Name: ____________________
UID ____________________
Part I. Single-choice questions (44 points)
1. Among all the bonds listed as below, which has the lowest bonding strength?
a. Bond between long-chain molecules in polymers
b. Bond between carbon-carbon atoms in diamond
c. Bond between carbon-chloride atoms in CCl4
d. Bond between carbon-hydrogen atoms in CH3Cl
2. What is the atom number for the simple hexagonal structure?
a. 2
b. 3
c. 4
d. 7
e. 14
3. Among the atomic bonds in the following materials, which one has the highest melting
point?
a. NaCl
b. CsCl
c. MgO
4. Which of the following terms defines the mass variations of an element?
a. Allotropy
b. Isotopes
c. Polymorphism
d. Ionization energy
5. As to a solid solution, how solvent atoms fit in solute atoms mainly depends on:
a. maintenance of electroneutrality
b. atomic bonding type
c. the difference in size between these atoms
d. Number of valence electrons
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MAE201: Materials Science, Summer 2022
6. Which of the following materials has the lowest boiling (or melting) point?
a. Carbon tetrachloride (CCl4)
b. Water (H2O)
c. Sodium chloride (NaCl)
d. Steel (Fe-C)
7. Which of the following items of an element is the most important factor affecting the
chemical reactivity of the element?
a. Neutron number
b. Number of isotopes of an element
c. Valence electrons
d. Number of shells
8. Which of the following features of the microstructure in steel explains why steel is
stronger than pure iron?
a. Uniform fine grains
b. Columnar grains
c. Addition of carbon atoms and the local stress field caused by carbon atoms
d. Carbon atoms being larger than iron atoms
9. Brass is a solid solution containing copper as the solvent and zinc as the solute
material. Which one of the following statements is NOT correct about brass?
(a) Adding more Zinc atoms to the solution will increase its strength.
(b) Increasing dislocation density will decrease its strength.
(c) The solvent crystal structure is maintained.
(d) Adding cold work to the solution will increase its strength.
10. Which of the following materials is NOT anisotropic?
(a) Single crystal silicon
(b) Polycrystal metals with uniform fine grains
(c) Polycrystal metals with grains elongated along one direction due to an external
load
(d) Single crystal metals
11. Which one of these tensile test results is most likely from testing a brittle material?
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MAE201: Materials Science, Summer 2022
12. Which of the following strategies will soften metals or metal alloys?
a) Diffusing carbon atoms into a low-C steel
b) Adding cold work to a metal/alloy.
c) Removing dislocations from a cold-worked metal/alloy through heat treatment
d) Adding boron atoms into pure single crystal silicon
13. Which of the following is the primary factor in determining if a sheet metal can be
bent and formed into another shape without experiencing fracture and other
undesirable defects (such as cracks)?
(a) Ultimate tensile strength
(b) Modulus of elasticity
(c) Ductility
(d) Fracture strength
(e) Hardness
14. Temperature can significantly affect the diffusion rate of a diffusion, because
(a) Temperature can change the concentration of solute atoms at the surface of a solvent
material
(b) Temperature can change the diffusivity
(c) Temperature can change the crystal structure of a solvent material
(d) Temperature can change the size of solute atoms
15. Which of the following features at microstructure level determines the amount of
plastic deformation a non-cold-worked metal can go through before fracture?
(a) Bonding energy between neighboring atoms
(b) Distance between neighboring atoms
(c) Number of slip systems
(d) The atomic number of a metal
16. What is the value of 40MPa called in the following figure (note that N represents the
number of operation cycles)?
(a) Yield strength
(b) Fracture strength
(c) Fatigue limit
(d) Ultimate tensile strength
(e) Resolved shear stress
17. Which of the following statements is NOT correct about toughness?
(a) The unit of toughness is the unit of work.
(b) Generally speaking, FCC materials have high toughness, while ceramics have low
toughness.
(c) By measuring toughness at different temperatures, DBTT can be found out from a
metal, if there is DBTT.
(d) If a material shows high toughness, this material must show high hardness.
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MAE201: Materials Science, Summer 2022
19. The reason that an annealing process can soften a cold-worked Fe-C alloy is:
a) The annealing process decreases the carbon content in the alloy
b) The annealing process increases the dislocation density of the alloy
c) The annealing process decreases the dislocation density of the alloy
d) The annealing process generates more barriers in the microstructure of the alloy to
prevent dislocation motion.
20. Which of the following belong to the applications of atomic diffusion?
a. Annealing of an iron-carbon system for reducing strength
b. Impurity diffusion in the semiconductor industry for making IC (integrated circuits)
c. Cold work on metals
d. Using grain refiners for obtaining fine grains
21. Which of the following features in the microstructure of a material will NOT
strengthen the material (or make the material stronger)?
a. Dislocations
b. Cracks
c. Grain boundaries
d. Addition of atoms of another type to the material
22. What does the Charpy test determine?
(a) Yield strength
(b) Fracture strength
(c) Young’s modulus
(d) Toughness
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MAE201: Materials Science, Summer 2022
Part II. Short-answer questions (6 points)
1. (2 points) What is the carbon content in 1050?
2. (4 points) List the following four materials according to their decreasing order of
toughness.
Polymers,
diamond,
1050 with 0% cold work,
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1012 with 0% cold work
MAE201: Materials Science, Summer 2022
Part III. Calculation (50 points)
1. (6 points) Find out the Miller indices for the crystal plane shown in the figure.
z
(3/4,0,1)
y
x
(1,1,0)
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MAE201: Materials Science, Summer 2022
2. (10 points) A metal has a BCC crystal structure. Its planar atomic density for the (110)
crystalline plane is 8.84 atom/nm2. Calculate:
1) The lattice constant;
2) The linear atomic density along the [111] direction;
3) The planar atomic density for the (100) crystalline plane.
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MAE201: Materials Science, Summer 2022
3. (10 points) Assume that the molar mass of a metal forming the body-centered tetragonal
crystal shown as below is 100g/mol. What is the volume density of this metal (Atoms are
treated hard spheres and have a radius of r=0.15nm)?
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MAE201: Materials Science, Summer 2022
4. (10 points) At 300ºC the diffusion coefficient for Cu in Si is measured to be D (300ºC) =
7.8 x 10-11 m2/s; at 400 ºC the diffusion coefficient for Cu in Si is measured to be D (400ºC)
= 28.5 x 10-11 m2/s.
1) What is the activation energy (Qd) for diffusion of Cu in Si;
2) What is the proportionality constant (D0) for diffusion of Cu in Si.
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MAE201: Materials Science, Summer 2022
5.(14 points) A stress of 100MPa is applied in the [110] direction on a BCC single
crystal. Calculate the resolved shear stress acting on the (111) [010] slip system.
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