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Flashcards in Phase Diagrams And Alloying Deck (35)
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1
Q

Do materials all have one example of each phase?

A

No. For example, Iron is polymorphic, carbon can be diamond or graphite, sugar can be crystals or candy.

2
Q

What are the two kinds of solid solutions?

Split this into multiple cards.

A

Interstitial. Which is a parent structure “Solvent” with much smaller “Solute” atoms in the gaps of the structure. There is also a limit on how many solute atoms into the structure (there is a solubility limit).

Substitutional. Which is a crystal structure with some of the atoms of one element replaced by atoms of a different element. This can be done, until all atoms are eventually replaced. The atoms must be of a similar size, and the elements must have the same crystal structure. Can have unlimited solubility.

3
Q

What causes the solubility limit to change?

A

Temperature.

4
Q

Define a phase?

A

A component within a system that has uniform physical characteristics.

5
Q

Solid phase is also called?

A

Alpha.

6
Q

What is the phase diagram of an alloy with complete solid solubility called?

A

Binary Isomorphous Phase Diagram.

7
Q

For any non-100% composition of Alpha, the material will melt at what temperature?

A

Across a range of materials between the melting temperature of both materials.

8
Q

What is the upper line of the range of melting temperatures on a Binary Isomorphous Phase Diagram called?

A

Liquidus.

9
Q

What is the lower line of the range of melting temperatures on a Binary Isomorphous Phase Diagram called?

A

Solidus.

10
Q

What is an “Interstitial” solid solution?

A

An interstitial solid solution is a parent structure “Solvent” with much smaller “Solute” atoms in the gaps of the structure. There is a limit on how many solute atoms into the structure (this is referred to as a solubility limit).

11
Q

What is a “Substitutional” solid solution?

A

A substitutional solid solution is a crystal structure with some of the atoms of one element replaced by atoms of a different element. This can be done until all atoms are eventually replaced. The atoms must be of a similar size, and the elements must have the same crystal structure. Can have unlimited solubility.

12
Q

What is a “Eutectic” composition?

A

The eutectic composition of certain alloys is the composition at which the entire alloy melts at a single temperature.

13
Q

True/False: The temperature at which an alloy with a eutectic composition melts at is higher than the melting temperature of either pure materials.

A

False. The melting temperature is actually lower than the melting temperature of either pure metal. The word Eutectic means easily melted.

14
Q

In a phase diagram what is the “Solvus” line?

A

The solvus line describes the point at which a material changes from a single solid phase to two solid phases.

15
Q

What is a “Eutectic Reaction”?

A

A eutectic reaction is the moment at which a single liquid phase transforms into two solid phases at once. This has a unique structure.

16
Q

What kind of solid solution is Steel?

A

Interstitial. Carbon atoms are much smaller than iron atoms so they are able to sit in the interstitial spaces of the iron crystal lattice.

17
Q

What percentage of carbon can steel contain?

A

Anywhere from 0.02% to 1.7% carbon. Anything above 1.7% is no longer considered steel, it is instead known as Cast Iron.

18
Q

How much carbon can Gamma Iron/Austenite contain?

A

Gamma Iron/Austenite can accommodate up to 1.7% carbon.

19
Q

What temperature can Gamma Iron/Austenite exist at?

A

Temperatures above 723*C.

20
Q

What crystal structure is Gamma Iron/Austenite?

A

FCC.

21
Q

How much carbon can Alpha Iron/Ferrite contain?

A

Alpha Iron/Ferrite can accommodate up to 0.02% carbon.

22
Q

What temperature can Alpha Iron/Ferrite exist at?

A

Between room temperature and 910*C.

23
Q

What crystal structure is Alpha Iron/Ferrite?

A

BCC.

24
Q

What is the other name for Cementite?

A

Iron Carbide.

25
Q

What is the other name for Gamma Iron?

A

Austenite.

26
Q

What is the other name for Alpha Iron?

A

Ferrite.

27
Q

True/False: Cementite is not a solid solution.

A

True.

28
Q

What composition is Iron Carbide?

A

6.67% Carbon. Single Solid Phase.

29
Q

What is the solubility limit of Carbon in FCC Iron?

A

1.7%.

30
Q

What is the solubility limit of Carbon in BCC Iron?

A

0.02%

31
Q

What is the Eutectoid point of steel?

A

The point at which solid Gamma Iron turns into both Alpha Iron and Cementite.

32
Q

What is the Eutectoid composition of steel?

A

0.8% Carbon.

33
Q

At what temperature does the Eutectoid reaction occur for steel?

A

723*C.

34
Q

True/False: The Eutectoid and Eutectic structures are considered a phase.

A

False. They are considered combinations of two phases.

35
Q

What is the alternate name for the Eutectoid Solid steel?

A

Pearlite.