Description of three stages of Annealing.

1. PRESENTED BY-
GAURAV SHUKLA

2. Annealing is one of the heat treatment process
in which the metal is heated to a temperature
above its recrystallization temperature, kept at
that temperature some time and then very slow
cooling to develop equilibrium structure in the
metal or alloy.
Annealing is a heat treatment that alters the
physical and sometimes chemical properties of a
material to increase its ductility and to make it
more workable.

3. To -
 Increase ductility
 Reduce hardness
 Remove internal stresses
 Increase toughness
 Decrease brittleness
 Decrease electrical resistance etc.

4. Annealing process consists of three stages such as–
1. Recovery
2. Recrystallization
3. Grain Growth

5. No change occurs in microstructures.
It occurs at low temperature.
During this point defects are created.
 Dislocations of opposite sign come together
annihilate each other.
Point imperfections and dislocations are
associated with strain energy.

6. Fig-1 Rearrangement of dislocations
Recovery

7. Strained grains becomes stress free, strain free
grains.
Microstructure at the end of recrystallization is
much similar to the original structure prior to the
cold working.
Recrystallization temperature- The temperature
at which the normal cold worked material
recrystallizes in one hour.
Recrystallization temperature is high in case of
metal having high melting point.
Recrystallization temperature - Iron-450oc
Steel- 727oc

8. Degree of cold work
Initial Grain size
Temperature of Cold Working
Purity or composition

9. It occurs due to the heating the
metal beyond the time given for
recrystallization.
Diffusion occurs between grain
boundaries.
This results in increase in grain
size.
Due to Grain growth larger
grains reduces the strength and
toughness of metal and curve
boundary becomes planar.
Grain growth is useful for single
crystal. Fig-1

10. Fig-2 Changes in Microstructure during
different stages of Annealing

11. Fig-3 Schematic Representation of cold worked and Anneal cycle
showing the effects of Properties and Microstructures

12. Textbook of Material Technology by O.P. Khanna
http://www.brighthhubengineering.com/manufacturing-technology
http://www.engineersedge.com/materials/annealing
http://info.lu.farmingdale.edu/depts/met/met205/ANNEALING.html