Quiz 2

Question 1

FCC Plane Stacking Sequence

Answer 1

ABCABC

Question 2

HCP Plane Stacking Sequence

Answer 2

ABAB

Question 3

Rank the density of metals, ceramics, and polymers from highest to lowest density.

Answer 3

Metals > Ceramics > Polymers

Question 4

Single Crystal

Answer 4

When the periodic arrangement of atoms (crystal structure) extends without interruption throughout the whole specimen

Question 5

Polycrystalline Materials

Answer 5

composed of many small, single crystals (grains)

Question 6

anisotropic

Answer 6

For most single crystals, properties vary with crystallographic orientation

Question 7

isotropic

Answer 7

for polycrystalline materials having randomly oriented grains, properties are independent of
crystallographic orientation

Question 8

What do we need to calculate theoretical density?

Answer 8

crystal structure, atomic weight, unit cell lattice parameters

Question 9

Polymorphism/Allotropy

Answer 9

when a material has more than one crystal structure

Question 10

solidifictaion

Answer 10

result of casting of molten material (heating up, then cooling down)

Question 10

What is x-ray diffraction used for?

Answer 10

determining crystal structure and interplanar spacing

Question 11

equiaxed grain

Answer 11

roughly same dimensions in all directions

Question 12

columnar grain

Answer 12

grains elongated in one direction

Question 13

grain boundaries

Answer 13

-regions between grains (crystals)
-crystallographic misalignment across a boundary
-slight atomic disorder —> high atomic mobility and chemical reactivity

Question 14

What are the 3 types of crystalline imperfections?

Answer 14

Point defects (0-D), Linear defects (1-D), Interfacial defects (2-D)

Question 15

Vacancies

Answer 15

Vacant atomic sites (missing)

Question 16

self-interstitial

Answer 16

host atoms positioned in interstitial positions between atoms (extra of same atom)

Question 17

Solid soln of B in A: Substitutional

Answer 17

Cu in Ni

Question 18

Solid soln of B in A: Interstitial

Answer 18

C in Fe

Question 19

Solid soln of B in A plus particles of a new phase (usually for larger concentrations of B)

Answer 19

second phase particle
-different composition
-often different structure

Question 20

Hume-Rothery Rules (conditions for forming substitutional solid solns)

Answer 20

1. Δr <15%
2. Similar ENS (proximity in periodic table)
3. Same crystal structure
4. Valences (all else being equal, a metal will have a greater tendency to dissolve a metal of a higher valence than one of lower valence)

Question 21

edge dislocation

Answer 21

-extra half plane of atoms inserted into structure
- burger’s vector perpendicular to dislocation line

Question 22

screw dislocation

Answer 22

-spiral planar ramp resulting from shear deformation
-hold bottom half of crystal and move top half back one atom space
- burgers vector parallel to dislocation line

Question 23

burger’s vector

Answer 23

-measure of lattice distortion
-space where there’s extra

Question 24

Twin Boundaries/Planes

Answer 24

interfacial (planar) defect which mirrors reflections of atom positions of one side of twin plane to the other side

Question 25

stacking faults

Answer 25

interfacial (planar) defects which occur when there is an error in the planar stacking sequence (ex. ABCABABC instead of ABCABCABC)

Question 26

catalyst

Answer 26

-increases rate of chemical reaction without being consumed -catalytic reactions normally occur at surface defect sites

Question 27

optical microscopy

Answer 27

-light shot through specimen -provides up to ~0.1 micrometer resolution

Question 27

what does the equilibrium number vacancy defect depend on?

Answer 27

temperature

Question 27

electron microscopy

Answer 27

-electrons in specimen are scanned -provides higher magnifications and better resolutions than optical microscopes