MATE 210 FINAL EXAM
PREPARATION QUESTIONS
WITH COMPLETE SOLUTIONS
What are interstitial sites? - Answer- The voids in-between atoms in the crystalline
structure
How many atoms are in a FCC unit cell? - Answer- 4
Are there any close packed planes in a BCC unit cell? - Answer- No; a true close-
packed plane has 6 nearest neighbors. The highest packed plane in BCC is the {110},
but this is not the close-packed plane
Why are the properties of polycrystalline materials most often isotropic? - Answer-
Although each individual grain in a polycrystalline material may be anisotropic, if the
grains have random orientations, then the solid aggregate of the many anisotropic
grains will behave isotropically
What kind of defect is a substitutional defect? - Answer- Point defect
What are vacancy defects? - Answer- When a host atom is missing from a normally
occupied site in a crystalline structure
What are the three types of dislocations? - Answer- Edge, screw, and mixed
Solvent in terms of solid solution is... - Answer- ...the element that is present in the
greatest amounts.
What kind of defect is a grain boundary? - Answer- Surface defect
What are interstitial atoms? - Answer- Impurity atoms that fill the void between host
atoms
What kind of defect is a dislocation? - Answer- Linear defect
What do dislocations in metals allow? - Answer- Material deformation
What has to be present for substitutional solutions? - Answer- 1) Impurity atoms must
have a valence that is the same as or less than the host material
2) Atomic diameters and electronegativities for both atom types must be similar
3) Impurity atoms substitute for host atoms
, 4) Both elements must have the same crystal structure
What does the burgers vector define? - Answer- The magnitude and type of lattice
distortion in a dislocation
State the 4 segments of the W. Hume Rothery rule. - Answer- 1) All else being equal, a
metal will have a greater tendency to dissolve a metal of higher valency than one of
lower valency
2) Close proximity in period table i.e. similar electronegativities
3) Same crystal structure for pure metals
4) ∆r (atomic radius) < 15%
A Rockwell Hardness test measures... - Answer- A material's resistance to localized
deformation
Charpy Impact test are used to help determine a metal's... - Answer- Transition Temp
and Toughness
Creep is... - Answer- The plastic deformation of a material at elevated temperatures due
to a load lower than its yield strength
Yield strength is determined by... - Answer- a) The stress at which dislocation starts to
move and increase in number
and
c) The point on the stress strain curve where the initial linear portion begins to curve
over
Tensile strength is determined by... - Answer- The maximum stress before failure
If you were building a guard-rail on a bridge in an area that can reach temperatures as
low as -20F, you would want to use a steel... - Answer- with a DBTT below -20F
(would only become brittle if it got colder than 20, but because it only gets as cold as 20,
it will not become brittle)
Cracks have a _____ effect on fracture toughness due to _____. - Answer- Detrimental;
their sharp points being stress concentrators
HCP metals are more brittle than FCC metals because.... - Answer- FCC metals have
more slip systems than HCP
Cold-working is.... - Answer- Deforming a metal at a temperature below its
recrystallization temperature
Cold-working strengthens a metal by.... - Answer- Increasing the number of dislocations
which then interfere with other dislocations
PREPARATION QUESTIONS
WITH COMPLETE SOLUTIONS
What are interstitial sites? - Answer- The voids in-between atoms in the crystalline
structure
How many atoms are in a FCC unit cell? - Answer- 4
Are there any close packed planes in a BCC unit cell? - Answer- No; a true close-
packed plane has 6 nearest neighbors. The highest packed plane in BCC is the {110},
but this is not the close-packed plane
Why are the properties of polycrystalline materials most often isotropic? - Answer-
Although each individual grain in a polycrystalline material may be anisotropic, if the
grains have random orientations, then the solid aggregate of the many anisotropic
grains will behave isotropically
What kind of defect is a substitutional defect? - Answer- Point defect
What are vacancy defects? - Answer- When a host atom is missing from a normally
occupied site in a crystalline structure
What are the three types of dislocations? - Answer- Edge, screw, and mixed
Solvent in terms of solid solution is... - Answer- ...the element that is present in the
greatest amounts.
What kind of defect is a grain boundary? - Answer- Surface defect
What are interstitial atoms? - Answer- Impurity atoms that fill the void between host
atoms
What kind of defect is a dislocation? - Answer- Linear defect
What do dislocations in metals allow? - Answer- Material deformation
What has to be present for substitutional solutions? - Answer- 1) Impurity atoms must
have a valence that is the same as or less than the host material
2) Atomic diameters and electronegativities for both atom types must be similar
3) Impurity atoms substitute for host atoms
, 4) Both elements must have the same crystal structure
What does the burgers vector define? - Answer- The magnitude and type of lattice
distortion in a dislocation
State the 4 segments of the W. Hume Rothery rule. - Answer- 1) All else being equal, a
metal will have a greater tendency to dissolve a metal of higher valency than one of
lower valency
2) Close proximity in period table i.e. similar electronegativities
3) Same crystal structure for pure metals
4) ∆r (atomic radius) < 15%
A Rockwell Hardness test measures... - Answer- A material's resistance to localized
deformation
Charpy Impact test are used to help determine a metal's... - Answer- Transition Temp
and Toughness
Creep is... - Answer- The plastic deformation of a material at elevated temperatures due
to a load lower than its yield strength
Yield strength is determined by... - Answer- a) The stress at which dislocation starts to
move and increase in number
and
c) The point on the stress strain curve where the initial linear portion begins to curve
over
Tensile strength is determined by... - Answer- The maximum stress before failure
If you were building a guard-rail on a bridge in an area that can reach temperatures as
low as -20F, you would want to use a steel... - Answer- with a DBTT below -20F
(would only become brittle if it got colder than 20, but because it only gets as cold as 20,
it will not become brittle)
Cracks have a _____ effect on fracture toughness due to _____. - Answer- Detrimental;
their sharp points being stress concentrators
HCP metals are more brittle than FCC metals because.... - Answer- FCC metals have
more slip systems than HCP
Cold-working is.... - Answer- Deforming a metal at a temperature below its
recrystallization temperature
Cold-working strengthens a metal by.... - Answer- Increasing the number of dislocations
which then interfere with other dislocations
