Chapter 4 Imperfections in Solid

Question 1

Types of Point Defects Metal

Answer 1

• Vacancies - vacant atomic sites in a structure

* Self Interstitials - extra atoms positioned in the voids of atomic sites

Question 2

Types of Point Defects in Alloys

Answer 2

• Substitutional

* Interstitial

Question 3

Describe W. Hume - Rothery Rule

Answer 3

It is a rule that sets the condition for the formation of Solid Solutions

1. Difference in radius should be ~15%
2. Same crystal structure
3. Similar valency
4. Similar electronegativity

Question 4

Describe Line Defect

Answer 4

• slip between crystal planes when dislocation moves
• indicated by Burger vector “b”
• Burger vector indicates the magnitude of dislocation

Question 5

Types of Line Defects

Answer 5

EDGE DISLOCATIONS
• burgers perpendicular to dislocation
• extra atom (plane) inserted in a crystal structure
• edge dislocation can move under stress to minimize energy

SCREW DISLOCATIONS
• burgers parallel to dislocation
• shears the plane

MIXED DISLOCATION

GRAIN BOUNDARIES

Question 6

Types of Plane Defect

Answer 6

TWIN BOUNDARY (Plane)
• reflection of atoms across the “twin plane”
• ABCBA

STACKING FAULT
• disorientation of the crystallographic plane
• ABCABC to ABCABA