Lecture 03/08/2022

Question 1

What is steel?

Answer 1

Iron-carbon system

Question 2

What are ferrous alloys?

Answer 2

Iron based, classification based on carbon content

Question 3

In a solid solution, where does carbon sit in a binary system?

Answer 3

Interstitial sites

Question 4

What does it mean that iron shows allotropy/polymorphism?

Answer 4

Exists at different lattice structures based on temperature

Question 5

Describe FCC steel.

Answer 5

• Austenite
• High packing density
• Fewer, larger voids
• Dissolves more carbon

Question 6

Describe BCC steel

Answer 6

• Ferrite
• Lower packing density
• Lattice voids are smaller
• Dissolves less carbon

Question 7

Pure iron is also known as?

Answer 7

Soft iron

Question 8

Iron-carbon system is also referred to as?

Answer 8

Iron carbide

Question 9

Describe the properties of pearlite

Answer 9

• Alternating layers of ferrite (alpha) and cementite (Fe3C)
• 8:1 ratio
• Colonies with layers in specific orientations
• Mechanical properties in between ferrite and cementite

Question 10

Why do layers occur with the formation of pearlite?

Answer 10

Carbon atoms need to diffuse minimal distances

Question 11

Eutectoid steels form?

Answer 11

Pearlite microstructure composed of ferrite and cementite

Question 12

Hypoeutectoid steels form?

Answer 12

Proeutectoid ferrite and pearlite

Question 13

Hypereutectoid steels form?

Answer 13

Proeutectoid cementite and pearlite

Question 14

The addition of other elements cause what change with the eutectoid?

Answer 14

Change in position with respect to temp and carbon concentration

Question 15

What are the benefits of alloying elements?

Answer 15

• Improve corrosion resistance

- Make more amenable to heat treatment