Chapter 9

Question 1

what is a phase diagram?

Answer 1

pictorial representations of the state of matter

Question 2

solubility limit

Answer 2

the amount of how much solute can be dissolved in a solvent at a given temp

Question 3

what conditions are pd created?

Answer 3

equilibrium and atmospheric, can’t always be realistically achieved

Question 4

binary pd

Answer 4

relate phases when two elements mix

Question 5

tertiary pd

Answer 5

relate phases when three elements mix

Question 6

sign for solid

Answer 6

alpha

Question 7

what occurs between solid and liquid of the Cu-Ni pd

Answer 7

two phase region, think slush

Question 8

liquidus temp

Answer 8

above this temp, everything is liquid

Question 9

solidus temp

Answer 9

below this temp, everything is solid

Question 10

what three things do we get out of a pd?

Answer 10

• phases present
• phase composition
• determination of phase amounts

Question 11

how to determine phase amounts of two phase region?

Answer 11

Inverse lever rule - the fraction of one phase is the opposite segment divided by the total length of the tie line

Question 12

eutectic point

Answer 12

at eutectic temp and composition, a liquid transforms into 2 different solids. all three phases exist at the same time - eutectic phase

Question 13

eutectic isotherm

Answer 13

temp of eutectic point, separates (alpha and beta) from two phase regions``

Question 14

solvus line

Answer 14

separates (alpha) and (beta) from (alpha and beta)

Question 15

alpha

Answer 15

solid solution, rich in element A with a little of element B, composition is different enough from the solid solution to be a separate phase

Question 16

pro-eutectic

Answer 16

any phase forming above the eutectic isotherm - also known as primary

Question 17

total isotherm

Answer 17

any phase forming below eutectic isotherm

Question 18

eutectic phase

Answer 18

what forms at eutectic temp

Question 19

Microstructure development

Answer 19

the type of microstructure that develops in the material depends on the composition of the alloy

Question 20

microstructure in (L) region just more than 0%

Answer 20

material is liquid, with mostly A and a little bit of B

Question 21

microstructure in (L + alpha) region just more than 0%

Answer 21

solid phase (alpha) starts to appear as temp lowers

Question 22

microstructure in (alpha) region just more than 0%

Answer 22

material cools down and liquid disappears

Question 23

what is a phase

Answer 23

anything that can be separated physically or chemically

Question 24

what happens as a liquid cools from L > L+a > a > a+B

Answer 24

creates solid alpha with a little bits of solid beta. as temp decreases beta phase precipitates out

Question 25

what happens as a liquid cools at eutectic composition?

Answer 25

in most alloys, a+B forms in a lamellar structure

Question 26

what happens as a liquid cools from L > a+L > a+B

Answer 26

alpha will start to solidify, then as you approach

Question 27

what happens as a liquid cools from L > a+L > a+B

Answer 27

alpha will start to solidify, then as you approach eutectic temp, alpha+beta will form lamellar structure since the last liquid to solidify has eutectic composition

Question 28

what is the most commonly used metal?

Answer 28

iron

Question 29

pure iron at room temp

Answer 29

BCC ferrite (alpha)

Question 30

what does pure iron convert to at 912C

Answer 30

ferrite converts to austenite or gamma iron (FCC)

Question 31

what does pure iron convert to at 1394C

Answer 31

austenite converts to delta ferrite (BCC)

Question 32

what happens to iron at 1538C

Answer 32

delta ferrite melts into liquid

Question 33

majority of Fe-C (steel) alloys have less than ____wt% C

Answer 33

6.7

Question 34

cementite

Answer 34

present at 6.7wt% C, Fe3C, not a solid solution but an intermetallic compound

Question 35

alpha ferrite - max C composition

Answer 35

BCC - C can go to interstitial positions so we can only dissolve0.022wt% C

Question 36

gamma austenite - max C composition

Answer 36

FCC - spacing of lattice changes from alpha ferrite so up to 2.14wt% C

Question 37

what happens above 2.14wt% C

Answer 37

Fe3C starts to form and remain stable

Question 38

eutectic reaction of FeC

Answer 38

L > gamma + Fe3C

Question 39

eutectoid reaction

Answer 39

one solid transforms into two solid phases

Question 40

austenite cannot exist at ______

Answer 40

room temp

Question 41

FeC eutectoid reaction

Answer 41

gamma > alpha + Fe3C gamma > pearlite

Question 42

pearlite

Answer 42

lamellar structure of alpha + Fe3C

Question 43

hypo-eutectoid alloy cooling

Answer 43

starts as austenite, primary alpha starts to form along grain boundaries, then austenite becomes pearlite (alpha+Fe3C)