Chapter 3 - Defects

Question 1

Types of defect

Answer 1

• 0D, Point defects
• 1D, Linear defects
• 2D, Planar defects
• 3D, Volume defects

Question 2

0D, Point defects

Answer 2

• atoms are either missing or in irregular places in the lattice
• E.G. Lattice vacancies, substitutional & interstitial impurities

Question 3

1D, Linear defects

Answer 3

• groups of atoms in irregular positions

- E.G. Screw and Edge dislocations

Question 4

2D, Planar defects

Answer 4

• the interfaces between homogeneous regions

- E.G. Grain boundaries, stacking faults & external surfaces

Question 5

3D, Volume defects

Answer 5

• these are extended defects

- E.G. Pores or Cracks

Question 6

What are impurities?

Answer 6

Atoms which are different from the host. Can be intentional or unintentional

Question 7

What are defects?

Answer 7

An effect used to create desired material properties without changing the composition

Question 8

What factors do Substitutional solid solutions depend on?

Answer 8

depends on factors for high solubility:

• Atomic size factor
• Crystal structures of the solute and solvent must be the same
• Electronegavtivities of the solute and solvent should be comparable

Question 9

What are the characteristics of Interstitial Solid Solutions?

Answer 9

radius of the solute should be a lot less than solvent radius due to the fact that for FCC, BCC, HCP the voids between the host atoms are quite small

Question 10

What are Dislocations?

Answer 10

• Linear defects, i.e. defects which produce distortion in the lattice
• E.G. Edge or Screw (Taylor or Burger) Dislocations

Question 11

What are Dislocation Cores?

Answer 11

The area around the line where distortion in the lattice occurs

Question 12

What are Grain boundaries?

Answer 12

The atomic mismatch in the regions where the grains meet