Iron unit cell Flashcards

1
Q

Ferrite

A

> interstitial solid soln of C in BCC α-Fe

> a = 0.286 nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is γ-Fe

A

FCC, a = 0.365nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is δ-Fe

A

BCC, a = 0.293nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What sites do carbon atoms occupy in ferrite? Why?

A

octahedral, there is less net average displacement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is elastic strain energy equal to?

A

The square of the displacement of the Fe atoms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Why is solubility of C in ferrite very small?

A

High elastic strain energy associated with placement of carbon in octahedral sites

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is austenite?

A

intersitial solid solution of C in FCC γ-Fe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why do carbon atoms occupy octahedral sites in FCC austenite?

A

The octahedral site voids are larger than the tetrahedral ones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The solubility of C in FCC austenite is ______ than that of C in BCC ferrite. Why?

A

much higher; the strain energy is substantially lower

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Cementite

A

> intermetallic line compund
Fe3C
density is similar to ferrite
it is a metastable phase, but won’t decompose into equilibrium phases ferrite and graphite because kinetics are slow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly