Exam 2

Question 1

Peierls stress/energy

Answer 1

point of max energy/shear stress

Question 2

slip plane

Answer 2

shear plane where dislocation formation and motion is possible

Question 3

slip plane

Answer 3

{hkl}

Question 4

slip direction

Answer 4

<uvw>
</uvw>

Question 5

elastic stress

Answer 5

main reason for higher energy when a dislocation happens

Question 6

activation energy, highest/lowest for?

Answer 6

highest: bcc systems
lowest: fcc systems

Question 7

Schmid factor (slip system)

Answer 7

slip system aligned with this factor: first one to activate when stress increases

Question 8

Gibbs free energy G

Answer 8

G = H - T . S

Question 9

enthalpy

Answer 9

H, sum of all energies in a system

Question 10

entropy

Answer 10

S, number of possibilities of a structure

Question 11

self-diffusion

Answer 11

atoms of a pure element jump around when T > 0 K

Question 12

impurity-diffusion

Answer 12

diffusion speed of the impurity is independent of the concentration

Question 13

inter diffusion

Answer 13

the mixing of elements in solid state

Question 14

interstitial-diffusion

Answer 14

smaller atoms jumping in between lattice sites, is very fast

Question 15

when does nuclei grow into crystals?

Answer 15

at melting temp Tm

Question 16

what does a finer grain structure increase?

Answer 16

increases yield strength, which increases toughness, but decreases ductility

Question 17

non-random grain structure

Answer 17

crystallographic texture

Question 18

climbing

Answer 18

dislocations moving up and down

Question 19

recovery

Answer 19

1. dislocations climb towards each other
2. annihilate with their partner
3. left over dislocations align to minimise strain energy

Question 20

forming small-angle grain boundaries

Answer 20

polygonisation

Question 21

recrystallisation

Answer 21

nucleation of new crystals

Question 22

cold-hardening

Answer 22

lowers toughness and fatigue resistance

Question 23

latent heat

Answer 23

energy absorbed/released during a phase change (no change in temperature)

Question 24

a-phase

Answer 24

solid phase

Question 25

tie line

Answer 25

horizontal line between two phase boundaries

Question 26

how to remove coring?

Answer 26

anneal the alloy at high temperature for diffusion mixing/annealing

Question 27

precipitates

Answer 27

b-particles within a-matrix

Question 28

solution annealing

Answer 28

reverting to pure phase by heating

Question 29

intermediate phases

Answer 29

little to no correclation to the pure element

Question 30

strictly stoichiometric

Answer 30

no existence range, horizontal line

Question 31

eutectic reaction

Answer 31

L <> a + b

Question 32

eutectoid reaction

Answer 32

d <> y + e

Question 33

peritectic reaction

Answer 33

d + L <> e

Question 34

congruent phase transformation

Answer 34

L <> y

Question 35

Gibbs phase rule

Answer 35

P + F = C + N

Question 36

at what temperature does iron change into an fcc lattice?

Answer 36

912 degrees

Question 37

austenite with slow cooling

Answer 37

pearlite + a-proeutectoid phase

Question 38

austenite with moderate cooling

Answer 38

bainite

Question 39

austenite with rapid cooling

Answer 39

martensite

Question 40

reheated martensite

Answer 40

tempered martensite

Question 41

pearlite forming

Answer 41

y <> a + Fe3C

Question 42

proeutectoid ferrite forming

Answer 42

a + y

Question 43

proeutectoid cementite forming

Answer 43

y + Fe3C

Question 44

iron phases

Answer 44

ferrite a, bcc austenite y, fcc delta ferrite d, bcc

Question 45

precipitation

Answer 45

forming b-phase in solidified a

Question 46

how does precipitation work?

Answer 46

1. heating the a-phase to high temperature 2. cooling it rapidly 3. reheating it to a normal temperature, where precipitates form in the a-matrix

Question 47

cementite

Answer 47

Fe3C