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Materials Science > Chapter 9 (Phase diagrams) > Flashcards

Chapter 9 (Phase diagrams) Flashcards

1
Q

What are the components?

A

the elements or compounds which are mixed initially

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2
Q

what are the phases?

A

the physically and chemically distinct material regions

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3
Q

what is the solubility limit?

A

maximum amount of solute that can go into solution in solvent. Also the maximum concentration for which a single phase can occur

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4
Q

what happens after the solubility limit is exceeded?

A

we have now created a 2 phase mixture

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5
Q

what is equilibrium

A

the state of lowest free energy, also the most stable one

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6
Q

what is particular about equilibrium phase diagrams

A

there are no rapid changes in state

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7
Q

what is a binary alloy?

A

a mixture of 2 metals

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8
Q

what is a ternary alloy?

A

a mixture of 3 metals

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9
Q

what characteristics should 2 metals have to become an alloy? (4)

A
  1. Both FCC
  2. similar size
  3. similar valence
  4. they should be good solubility
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10
Q

how do we determine the composition of a mixture of phases from a phase diagram?

A

from the point we draw a line across to each phse a down from those points to the x-axis, those values will give us the respective compositions

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11
Q

describe how to use the tie line?

A

the numerator will always be the distance AWAY from the phase youre trying to determine

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12
Q

what is the liquidus line

A

the line ABOVE which ONLY LIQUID is present

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13
Q

what is the solidus line

A

the line BELOW which ONLY SOLID is present

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14
Q

what can be said about solid state diffusion

A

takes more time and temperature

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15
Q

what can be said about the grain structure during equilibrium cooling

A

the grains would be uniform

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16
Q

what would happen if the material was cooled very quickly?

A

the final grain composition would not be uniform, aka “CORED” grains

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17
Q

what are cored grains

A

when we cool a materials very quickly, the inner layer has a different composition from the outer layer

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18
Q

what is a eutectic reaction?

A

when a liquid is transformed into 2 different solid phases

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19
Q

how many phases are there at the eutectic line?

A

3

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20
Q

how are fixed compositions represented?

A

by vertical lines on phase diagrams

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21
Q

what is eutectic?

A

a liquid in equilibrium with two solids (L alpha + Beta)

22
Q

what is eutectoid

A

solid phase in equilibrium with 2 other solids phases

a –» Beta+gamma

23
Q

what is peritectic

A

liquid+solid 1 —> solid 2

24
Q

in the Iron carbon system what is alpha?

A

ferrite. an interstitial solid solution of carbon in BCC iron

25
in the Iron carbon system what is gamma?
austenite, an interstitial solid solution of carbon in FCC iron
26
in the Iron carbon system what is Fe3C
cementite
27
in the Iron carbon system what is delta
ferrite, an interstitial solid solution of carbon in BCC iron
28
what is the eutectic temperature in the iron carbon phase diagram?
1147 C
29
what is the eutectoid temperature in the iron carbon phase diagram
727 C
30
what type of steel is less than 0.76 weight percent
HYPO-eutectoid
31
what type of steel is 0.76 wt% C
eutectoid steel
32
what type of steel is >0.76 wt% C
HYPER-eutectoid
33
what is pearlite and in what type of reaction is this formed
alpha + Fe3C, Eutectoid reaction
34
how can we increase the solubility limit
by increasing the temperature
35
what do equilbrium diagram basically show us
what phases are present at equilibrium
36
what has to be the case for solid state diffusion to take place
it requires a lot of time and temperature, so we must cool it very slowly to allow diffusion to take place
37
what can be said about the percent composition of phase if we cool a solid with non-equilibrium cooling
we know there must be a greater percentage of liquid than for equilibrium cooling
38
what process can we use to remove coring
homogenization
39
True of false, the eutectic composition freezes at a higher temperature than other composition
false, lower
40
how can we describe the grain diagram at the eutectic temperature
alternating layers of alpha and beta crystals (hatched bars)
41
if there is more of the L+alpha phase than the L+beta phase when the eutectic temperature is reached, then will it be hypo or hyper eutetectic
hypo
42
which type of structure are favored eutectic reactions
ones that have higher interfacial areas, eg: lamellar, rod-like, globular. They aren't usually equiaxed grains
43
graphically, what is the effect of solid solution strengthening on tensile strength and ductility respectively
upward parabola for tensile strength, and downward parabola for ductility
44
List the number of single phase regions and 2-phase regions in Binary Eutectic phase diagrams
single phase: 3 | 2-phase: 3
45
what are the solid solutions at the sides of the phase diagram called?
Terminal Phases
46
How do intermetallic compounds appear on phase diagrams?
AS VERTICAL LINES
47
Furthermore, what can be said about intermetallic compounds in terms of their composition?
they have FIXED composition
48
what is the peritectic temperature?
1493 deg C
49
true of false, eutectoid reactions don't involve liquids
true
50
name the 2 important points for the IRON-CARBON phase diagram
1. Eutectic: L ->> gamma +Fe3C @1147 deg C 2. Eutectoid: gamma ->> alpha +Fe3C @ 727 deg C
51
which structure is the easiest for Pearlite?
Lamellar structure
52
if we add other elements to the Fe-Fe3C diagram what can happen?
- eutectoid temp can move up or down | - eutectoid can move to higher or lower carbon concentrations

Materials Science (13 decks)

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