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Mat E 202 > Ch 8 > Flashcards

Ch 8 Flashcards

1
Q

Define equilibrium

A

Changes are carried out slowly enough that the phases in the system have the same properties everywhere and there are no concentration gradients

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2
Q

Is diffusion faster, slow in solids

A

Slow

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3
Q

Define phase

A

A region of matter which has homogeneous physical and chemical properties

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4
Q

Define phase diagram

A

A graphical representation (map) of the phases present with variations in temperature in composition, when thermodynamic equilibrium has been achieved

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5
Q

Define polyphase materials

A

Materials containing two or more coexisting phases

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6
Q

4 things that the properties of polyphase materials depend on

A
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7
Q

Define components

A

The elements (atoms), molecules, or compounds, which are initially mixed

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8
Q

Define solute

A

Present in minor concentration

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9
Q

Define solvent

A

Present in major concentration

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10
Q

Define solubility limits

A

The max concentration of solute that may be added, without forming a new phase

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11
Q

Define metastable

A

Nonequilibrium state, which may persist for a very long time

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12
Q

Are metastable phases, shown on phase diagrams

How can they be formed?

A

No

Can be formed due to rapid cooling

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13
Q

Define isomorphous

A

Having the same structure

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14
Q

What does isomorphous mean in terms of phase diagrams?

A

Isomorphicity is having the same crystal structure in the solid phase and complete solid solubility for all compositions

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15
Q

Binary phase diagrams: what happens when a mixture exhibit clustering in the solid

A

A miscibility gap

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16
Q

What does a binary phase diagram show?

A

The phases present at equilibrium of two different elements

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17
Q

Describe the binary phase diagram

(Where liquid and solids are and the liquidus line and solidus line)

A
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18
Q

Define solidus line

(2 definitions)

A

Line on the phase diagram, where solidification is complete upon equilibrium cooling

Where melting begins upon heating

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19
Q

In heating what’s line must you stay below?

A

Solidus line

Or it will lose its shape by partial melting

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20
Q

Define liquidus line

(2 definitions)

A

Line on a phase diagram above, which melting of a solid is complete upon heating

Where solidification begins upon cooling

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21
Q

In melting an alloy what do you need to do if you want a homogeneous liquid

A

Must exceed the liquidus line

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22
Q

Define system composition/overall composition

A

How much of each element is present in total?

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23
Q

What variable represents system composition?

A
24
Q

Define Tieline

A

A horizontal line constructed across a two phase region of binary phase diagrams 

25
Q

What does the tie line intersect on either end?

A

The phase boundaries that represent the equilibrium composition at the given temperature in the question

26
Q

Steels: what are the two Greek letter symbols for the solid phases

A
27
Q

Define phase constitution

(3 things)

A

The number and types of phase is present

The composition of each phase

The amount of each phase

28
Q

Describe the three things you get from a tie line

A



29
Q

What does the evolution of the microstructure depend on?

A

How rapidly the system is cooled

30
Q

Can you see microstructure under a microscope?

A

Yes

31
Q

Three things that micro structure includes

A

Phase constitution

Morphology and spatial distribution of phases

32
Q

What does the evolution of the microstructure depend on?

A

How rapidly the system has cooled from high temperature

33
Q

Phase diagrams: as a liquid solution is cooled it will start solidifying at what line

A

Liquidus line

34
Q

Phase diagrams: what leads to concentration gradients in grains

A

The change in concentration with decreasing temperature if cooling is rapid

35
Q

Phase diagrams: what happens if we cool slowly enough

A

The grains at formal experience diffusion in the concentration gradient, due to compositional changes during cooling will be illuminated

36
Q

Phase diagrams: at true equilibrium what can be said about the composition and structure of each phase

A

They are spatially uniform

37
Q

Phase diagrams: why is the composition of the solid and liquid phase is changing as a system is cooled

A

Because the liquidus and solidus lines have a slope to them

38
Q

Define eutectic

A

Easily melted

39
Q

Eutectic phase diagrams: define invariant point

A

Where there is an equilibrium between the two phase solid region, and a liquid

40
Q

Eutectic phase diagrams: what happens upon heating?

A

Liquid starts to format the eutectic temperature

41
Q

What variable represents eutectic temperature?

A
42
Q

What type of phase diagram is this?

A

Binary eutectic phase diagram

43
Q

Label the six different lines

A
44
Q

What do the blue arrow show?

A

The max solid solubility for the single phase solids

These compositions are the endpoints of the eutectic isotherm

45
Q

What is the most common eutectic structure?

A

Lamellar eutectic

46
Q

What are the hypo and hyper eutectic compositions based on?

(Binary eutectic, phase diagrams)

A

Based on the component on the left side, being the solvent in the component on the right side, being the solute

47
Q

Define hypo, eutectic composition

A

Are the range of compositions above the solubility limit of being a at the eutectic temperature up to, but less than the eutectic composition

48
Q

In terms of hypo and hyper, which one means less, and which one means more

A

Hypo equals less

Hyper equals more

49
Q

Define hypereutectic composition

A

The range of compositions above the eutectic composition up to the solid solubility limit of ANB at the eutectic temperature

50
Q

Define the pro eutectic phase

A

The first phase to start solidifying from the liquid upon cooling for a hypo or hyper eutectic overall composition

51
Q

What is the notation for pro eutectic?

(And other name)

A

Primary phase

52
Q

At what temperature does the protective phase form?

A

Add temperatures above the eutectic temperature, but below the liquidus

53
Q

Binary, eutectic diagram: where is the

hypo eutectic

Eutectic

Hypereutectic

A
54
Q

A eutectoid reaction is similar to a eutectic reaction, except for what

A

The high temperature liquid phase replaced by another solid phase so that the whole reaction is in solid state

55
Q

Define eutectoid reaction

A

Upon cooling one solid phase, transforms, isothermal, he and reversibly into two new solid faces that are intimately mixed

56
Q

Define eutectic reaction

A

Upon cooling a liquid phase transforms, isothermal, he and reversibly into two intimately mixed solid faces

57
Q

Defined the proeutectoid phase (primary phase)

A

A solid that starts to nuclear at a service line rather than at the liquidus line

Mat E 202 (10 decks)

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