Strengthening Mechanisms in Construction Steel and Aluminum Alloys

Question 1

How do you do precipitation hardening?

Answer 1

Quench from alpha into alpha +beta and then heat up a little while remaining in alpha + beta

Question 2

How do you do Work Hardening?

Answer 2

• Deformation causes dislocation entanglement; i.e. pinning of dislocations
Number of dislocations are increased by cold work

Question 3

What does cold worked steel lead to?

Answer 3

1 recovery - dislocations move and are relocated int structure

2 recrystallization - new grains nucleate at cell boundaries of polygonized structure
• If metal is held at crystallization temperature long enough, cold worked structure is completely replaced with recrystallized grain structure.

3 Grain growth- reduce high energy associated with large number of grain boundaries

Question 4

What are factors that affect recrystallization?

Answer 4

Amount of prior deformation
Temperature and time
Initial grain size
Composition of metal