Part 7: Dislocations and Strengthening

Question 1

Plastic deformation occurs by motion of ____

Answer 1

Dislocations

Question 2

T/F: Grains change shape after plastic deformation

Answer 2

True

Question 3

What are the 3 mechanisms of strengthening solid materials

Answer 3

1. Grain size reduction
2. Solid solution strengthening
3. Strain hardening / cold working

Question 4

How does reducing the grain size strengthen materials?

Answer 4

Grain boundaries are barriers to dislocation motion, so smaller grains adds more barriers and reduces the range of motion for dislocations

Question 5

For solid solution strengthening, where would a small interstitial atom go in crystal structure?

Answer 5

One atom in area with tensile stress

Or multiple atoms at compressive area of slip plane

Question 6

What is cold working?

Answer 6

Plastic deformation at room temperature to increase the yield strength of materials