Chapter 10

Question 1

What is a phase?

Answer 1

A portion of a material that its physical and chemical characteristics are homogeneous.

Question 2

Three microstructural characteristics that are important for multiphase alloys are:

Answer 2

The number of phases present
The relative proportions of the phases
The manner in which the phases are arranged

Question 3

Three factors that affect the microstructure of an alloy:

Answer 3

What alloying elements are present
The concentrations of these alloying elements
The heat treatment of the alloy

Question 4

One-component Phase Diagram consists of:

Answer 4

Solid, liquid and gas of a single element

Question 5

Binary Isomorphous diagram

Answer 5

Phase Diagram with two components in which there is complete solubility in the solid phase

Question 6

Binary Phase Diagram

Answer 6

Two components are present and the variables are Composition (wt%) and Temperature (C)

Question 7

Binary Eutectic Phase Diagram

Answer 7

Lines are shaped in a v and the phase goes from Liquid to two solids (L -> a + b) as the temperature cools at the eutectic composition.

Question 8

3 Tricks in interpretating the phase diagram

Answer 8

1) What phases are present
2) Composition of each phase (draw tie lines and drop down at intersections)
3) Amount of each phase (inverse lever rule: draw tie line and take the opposite length of the line over the total length of the tie line to get the amount of the composition of the phases at that point).

Question 9

Eutectoid

Answer 9

Same shape as Eutectic, but Liquid is not on top of the eutectoid temperature

Question 10

Eutectoid composition for iron-iron carbide alloy

Answer 10

0.67%

Question 11

3 alloys of iron-iron carbide alloys:

Answer 11

Irons (<0.008 wt% C)
Steels (0.008 to 2.14 wt% C)
Cast irons (>2.14 wt% C)

Question 12

Phases of Iron-Iron carbide phase diagram

Answer 12

alpha: ferrite (BCC)
gamma: Austenite (FCC)
Cementite: Fe3C

Question 13

What is Pearlite?

Answer 13

The microstructural product of an iron–carbon alloy of eutectoid composition, producing a microconstituent consisting of alternating layers of ferrite and cementite.

Question 14

What is in the hypo-eutectoid microstructure

Answer 14

proeutectoid ferrite (alpha chunks) and pearlite (alternating layers)

Question 15

What is in a hyper-eutectic microstructure

Answer 15

proeutectic cementite and pearlite