CH 9 - Phase Diagrams

Question 1

What is a solution?

Answer 1

single phase solid, liquid or gas

Question 2

What is a mixture?

Answer 2

more than one phase present

Question 3

What is a solubility limit?

Answer 3

max concentration for which only a single phase solution exists

Question 4

What is a tie line?

Answer 4

• connects the phases in equilibrium with each other

- also called an isotherm

Question 5

What is the resulting structure from slow cooling?

Answer 5

equilibrium (uniform) structure

Question 6

What is the resulting structure from fast cooling?

Answer 6

cored structure

Question 7

What is a eutectic microstructure?

Answer 7

alternating layers of alpha and beta phases

Question 8

Define eutectic

Answer 8

liquid transforms to two solid phases

Question 9

Define eutectoid

Answer 9

one solid phase transforms to two other solid phases

Question 10

Define peritectic

Answer 10

liquid and one solid phase transform to a second solid phase

Question 11

What is the solvus line?

binary eutectic

Answer 11

solid solubility limit line separating the alpha & alpha plus beta phase regions

Question 12

What is the solidus line?

binary eutectic

Answer 12

boundary between the alpha & alpha plus L fields

Question 13

What is the liquidus line?

binary eutectic

Answer 13

temp where alloy becomes totally liquid

Question 14

Define ferrite

Answer 14

room temp, stable alpha iron with BCC

Question 15

Define austenite

Answer 15

gamma iron with FCC

Question 16

Define cementite

Answer 16

intermediate compound of iron carbide

Question 17

What is the eutectic reaction for the iron-iron carbide system?

Answer 17

Liquid –> austenite (gamma iron) plus Fe3C

Question 18

What is pearlite?

Answer 18

• microstructure for eutectoid steel
• formed when slowly cooled through the eutectoid temp
• consists of alternating layers of the two phases that form simultaneously during the transformation