1. Description & importance
CRYSTAL DEFECTS
Description & importance

2. FUNDAMENTALS
Metals are not perfect neither at the macrolevel and nor at the microlevel
Contain a number of different types of crystalline defects (at the atomic level)
Defects are important in many processes e.g. diffusion, deformation

3. TYPES OF DEFECTS A. POINT DEFECTS OR ZERO-DIMENSIONAL DEFECTS
In pure metals
In alloys
1. VACANCY
2. SELF-INTERSTITIAL
1. SUBSTITUTIONAL IMPURITY
2. INTERSTITIAL IMPURITY
Important in strengthening
Important in diffusion

4. Mechanism of diffusion
VACANCY

5. B. Line defects or one-dimensional defects
Edge dislocation
Screw dislocation
VERY IMPORTANT IN PLASTIC DEFORMATION

6. C. Planar (surface) defects or two-dimensional defects
1. Stacking Fault
Perfect stacking
Extrinsic stacking fault
Intrinsic stacking fault A A A A B B A A A A B B B B A A A A C C C C B B B B A A A A C C C C B B A A A A C C C C B B B B A A A A

7. 2. Grain Boundaries

8. D. Volume defects or three-dimensional defects
Some scientists classify grains as volume defects

9. QUESTIONS

10. Some basics on alloys Two types Compounds E.g. Fe3C, CuAl2
Solid solutions
Substitutional
Solid solution
E.g. Brass (Cu-Zn)
Cu-10%Zn or Cu-30%Zn
Interstitial
Solid solution
E.g. Steel (Fe-C)
Fe-0.2%C or Fe-0.4%C Cu Zn Fe C

11. PHASE DIAGRAMS