MAE 2381 FINAL REVIEW EXAM
QUESTIONS AND ANSWERS LATEST
UPDATE
What is the coordination number for a corner atom in the BCC crystal structure? -
ANSWER8
What is the coordination number for the FCC crystal structure? - ANSWER12
The stacking sequence for the FCC crystal structure is (ABABAB/ABCABC)? -
ANSWERABCABC
How many atoms/unit cell are there for BCC crystal structure? - ANSWER2
How many atoms per unit cell are there in the HCP structure? - ANSWER6
The delocalized electrons in metals make them good conductors of -
ANSWERElectricity or heat
List all of the primary interatomic bond types that are directional - ANSWERCovalent
Van der Waals bonding depends on the separation of positive and negative charges,
referred to as a (blank). The bond strength for Van der Waals bonding is
(stronger/weaker) than metallic bonding. - ANSWERDipoles
Weaker
How many lattice points/unit cell are there in the hexagonal lattice? - ANSWER3
Vacancies exist because they increase the (Gibbs free energy/entropy) of the
material - ANSWEREntropy
An (octahedral/tetrahedral) interstitial impurity at is surrounded by 6 host atoms. -
ANSWEROctahedral
Hume-Rothery Rules - ANSWERCrystal structure- should be the same
Electronegativity- needs to be similar
Valences- higher tendency to dissolve higher valency.
Vacancies exist because they decrease the (gibbs free energy/entropy) of the
material - ANSWERGibbs Free Energy
An (octahedral/tetrahedral) interstitial impurity atom is surrounded by 4 host atoms -
ANSWERTetrahedral
, Diffusion through the lattice occurs (faster/slower) than diffusion at the grain
boundaries - ANSWERSlower
What is happening at the atomic level when a load is applied, that results in purely
elastic deformation? - ANSWERStretching of atomic bonds
Changing interatomic spacing
Plastic deformation is a result of the motion of - ANSWERDislocations
As the temperature of a metal increases, the modulus (increases/decreases) -
ANSWERDecreases
Interstitial diffusion is (faster/slower) than vacancy diffusion - ANSWERFaster
Vacancy diffusion is (faster/slower) than interstitial diffusion - ANSWERSlower
Slip in a single crystal will occur when the (blank) shear stress is greater than the
(blank) shear stress - ANSWERResolved
Critical Resolved
In general, a higher schmid factor will cause yield at a (higher/lower) applied stress -
ANSWERLower
A polycrystalline material is stronger than a single crystal of the same material
because grain boundaries - ANSWERinterfere with slip/dislocation motion
Recovery is usually sufficient to restore the electrical and thermal properties that
have been disrupted by cold work. (true/false) - ANSWERTrue
What is one reason that we would want to perform re-crystallization in a material? -
ANSWERRecover pre-cold worked conditions.
Increase ductility
If the amount of cold work is too (low/high) there will not be enough of a driving force
for recrystallization to occur - ANSWERLow
Why does grain growth occur at elevated temperatures? - ANSWERGrain growth
reduces number of grain boundaries which reduces internal energy/gibbs free
energy
Identify and explain 2 strengthening mechanisms for metals - ANSWERGrain size
reduction- smaller grains results in more grain boundaries that can interfere with slip.
Solid solution strengthening- impurity atoms interact with dislocations (lattice strain)
making slip harder.
Strain hardening- CN increases dislocation density, which makes it harder to move
dislocations.
For creep, why does creep strain decelerate in the first stage of creep? -
ANSWERStrain hardening slows down creep rate
QUESTIONS AND ANSWERS LATEST
UPDATE
What is the coordination number for a corner atom in the BCC crystal structure? -
ANSWER8
What is the coordination number for the FCC crystal structure? - ANSWER12
The stacking sequence for the FCC crystal structure is (ABABAB/ABCABC)? -
ANSWERABCABC
How many atoms/unit cell are there for BCC crystal structure? - ANSWER2
How many atoms per unit cell are there in the HCP structure? - ANSWER6
The delocalized electrons in metals make them good conductors of -
ANSWERElectricity or heat
List all of the primary interatomic bond types that are directional - ANSWERCovalent
Van der Waals bonding depends on the separation of positive and negative charges,
referred to as a (blank). The bond strength for Van der Waals bonding is
(stronger/weaker) than metallic bonding. - ANSWERDipoles
Weaker
How many lattice points/unit cell are there in the hexagonal lattice? - ANSWER3
Vacancies exist because they increase the (Gibbs free energy/entropy) of the
material - ANSWEREntropy
An (octahedral/tetrahedral) interstitial impurity at is surrounded by 6 host atoms. -
ANSWEROctahedral
Hume-Rothery Rules - ANSWERCrystal structure- should be the same
Electronegativity- needs to be similar
Valences- higher tendency to dissolve higher valency.
Vacancies exist because they decrease the (gibbs free energy/entropy) of the
material - ANSWERGibbs Free Energy
An (octahedral/tetrahedral) interstitial impurity atom is surrounded by 4 host atoms -
ANSWERTetrahedral
, Diffusion through the lattice occurs (faster/slower) than diffusion at the grain
boundaries - ANSWERSlower
What is happening at the atomic level when a load is applied, that results in purely
elastic deformation? - ANSWERStretching of atomic bonds
Changing interatomic spacing
Plastic deformation is a result of the motion of - ANSWERDislocations
As the temperature of a metal increases, the modulus (increases/decreases) -
ANSWERDecreases
Interstitial diffusion is (faster/slower) than vacancy diffusion - ANSWERFaster
Vacancy diffusion is (faster/slower) than interstitial diffusion - ANSWERSlower
Slip in a single crystal will occur when the (blank) shear stress is greater than the
(blank) shear stress - ANSWERResolved
Critical Resolved
In general, a higher schmid factor will cause yield at a (higher/lower) applied stress -
ANSWERLower
A polycrystalline material is stronger than a single crystal of the same material
because grain boundaries - ANSWERinterfere with slip/dislocation motion
Recovery is usually sufficient to restore the electrical and thermal properties that
have been disrupted by cold work. (true/false) - ANSWERTrue
What is one reason that we would want to perform re-crystallization in a material? -
ANSWERRecover pre-cold worked conditions.
Increase ductility
If the amount of cold work is too (low/high) there will not be enough of a driving force
for recrystallization to occur - ANSWERLow
Why does grain growth occur at elevated temperatures? - ANSWERGrain growth
reduces number of grain boundaries which reduces internal energy/gibbs free
energy
Identify and explain 2 strengthening mechanisms for metals - ANSWERGrain size
reduction- smaller grains results in more grain boundaries that can interfere with slip.
Solid solution strengthening- impurity atoms interact with dislocations (lattice strain)
making slip harder.
Strain hardening- CN increases dislocation density, which makes it harder to move
dislocations.
For creep, why does creep strain decelerate in the first stage of creep? -
ANSWERStrain hardening slows down creep rate
