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1. ARBA MINCH UNIVERSITY
INSTITUTE OF TECHNOLOGY
FACULTY OF MECHANICAL ENGINEERING
Presentation on: Annealing Processes
By: Melese .A
January, 2024
Arbaminch,Ethiopia

2. Outline
Unit Two
 Stage of annealing processes
 Driving force in annealing processes
 Factors of annealing processes
 Property change in annealing processes
 N-G aspect in annealing processes
 Annealing twin
 Texture in Cold worked and annealed alloy

3. Annealing
 Annealing is a heat treatment process designed to
eliminate the effects of cold working.
 And the properties of a metal may revert back to the
pre-cold worked states by Annealing.
Processes
 It is heating cold worked metal to a temperature above
recrystallization temperature, holding there for some
time and then slow cooling.

6.  Recovery the 1st
stage of annealing when a metal is
heated to a temperature below its melting point to
remove :
 Internal stresses
 Dislocations
 And restore its ductility, conductivity...
a) Recovery

7. a) Deformed metal b) Recovered metal

8.  Atom migration: The heat provides energy to the atoms in
the crystal lattice, allowing them to migrate.
 Dislocation removal: The migrating atoms remove
dislocations, or irregularities, in the metal's structure.
 Stress relief: The dislocations are moved into stress-free

10. Polygonization is a process that occurs during annealing when
excess dislocations arrange themselves into lower energy
configurations.
This happens when the number of dislocations of two signs are
unequal during deformation.
The result is regular arrays or low angle grain boundaries.
Polygonization

12. It is a process of arranging excess edge dislocations in the form of
tilt boundaries.
the excess screw dislocations in the form of twist boundaries,
with the resultant lowering of the elastic strain energy.

14.  It is nucleation and growth of new equiaxed and strain-free
crystals.
 Nucleation Small grains, or nuclei, form in areas of high
dislocation density.
 Growth The nuclei grow across regions of high dislocation
density, replacing the distorted structure.
 Completion The original grain structure is completely
replaced by new grains that are free from stress and
dislocation.
b) Recrystallization

16.  It is process of uniform increase in the average grain size and
decrease the number of grains in a material by eliminating grain
boundaries.
c) Grain Growth

17. Normal grain growth, the size of individual grains are
relatively uniform.
Abnormal grain growth, the differences in individual sizes of
the grains and randomly-oriented fine grains.
 some very large grains present along with the fine grains.
 E.g. Abnormal grain growth in in an Al–Mg–Sc–Zr alloy

18. a) Normally growth grain b) abnormally growth grain

19. Driving force in stage of annealing process
Recovery The reduction of stored energy due to cold
deformation.
Recrystallization The reduction of stored internal energy, mainly
from the reduction of dislocation density.
Grain growth The minimization of energy associated with grain
boundaries.

20. Factors influence annealing process
(1) Amount of deformation
(2) Temperature
(3) Time
(4) Initial grain size
(5) Composition
(6) Amount of recovery or polygonisation
(7) Method of deformation.

21. Properties change During stage of annealing processes
The purpose of annealing is to eliminate strain hardening and put the
material into a relatively soft, ductile condition.

22. Annealing Twins
 Annealing twin is formed in recrystallization stage of annealing
due to Growth accidents.
 Annealing twins form when a grain boundary migrates, rather
than from slip activity within grains.
 Annealing twins, most prevalent in Face Centered Cubic (FCC)
metals
 e.g. aluminum, copper, brass & iron with austenite etc.

24. Texture in Cold-Worked and annealed Alloys
 Texture refers to the crystallographic orientation of grains in a
material.
 During cold work and annealing, the changes in the microstructure
of the alloy, including the size and orientation of the grain, grain
boundary characteristics, and texture components, will
significantly affect the mechanical properties of the material

25. Texture in Cold-Worked Alloys Texture in Annealed Alloys
 Elongated and distorted grains.
 Deformation texture due to slip
systems.
 High strength and hardness.
 Reduced ductility.
 Equiaxed, strain and
dislocation -free grains.
 Restored ductility.
 Reduced strength and
hardness.

26. Thank You
.