2. NAME : SIVAKANALI.S
ROLL NO : 117011305043
DEPT : M.TECH(INT) II-yr.
SUB :XGS407(TECHNICAL
COMMUNICATION)
)
.
3. INTRODUCTION
An imperfection in a crystal’s lattice
structure either a missing atom or ion
creating vacancy in lattice or an extra
atom or ion between two normal lattice
points creating an interstitial.
4. CRYSATL DEFECTS
1.PERFECT ORDER doesn’t exist
throughout a crystalline material on a
atomic scale.
2.It influence properties such as
MECHANICAL,ELECTRICAL, MAGNETIC
3.All crystalline materials contain large
number of various defects or
imperfection.
7. VACCANCY
Missing
atom from
an atomic
site
1 2
• Atoms around
vacancy
displaced
3
• Tensile stress
field produced
in the vicitnity
4
• When
temperature
increases
vacancy will be
created
8. IMPURITY OF ATOMS
INTERSTITIAL Foreign atom positioned between
atomic site.(e.g) C in BCC iron.
SUBSTITUTIONAL
Foreign atom that substitutes for or
replaces a parent atom in the crystal.
Pentavalent or trivalent impurity atoms
doped in Si or Ge are also substitutional
impurities in a crystal.
9. LINE DEFECT_ DISLOCATION
In early 1900’s scientist observed that
metals undergo plastic deformation at forces
much smaller than the forces that are holding
the metal atoms together.
they postulated that there are some
defects(dislocations),which is bringing down the
stress required for the plastic deformation.
10. DISLOCATIONS
Many mettallurgists remained skeptical of the
dislocation theory until the development of the
transmission electron microscope (TEM) in the late
1950’s.
TEM allowed experimental evidence to be collected that
showed that the strength and ductility of the metals are
con trolled by the dislocations.
11. Edge dislocations :
E
D
G
Extra half-plane of
atoms is introduced
midway through
crystal
Dislocation motions
requires movement in
baby steps.
When force applied from
one side of the crystal ,the
extra plane passes through
planes of atoms breaking
and joining bonds with
them until it reaches the
grain boundary.
Bond across the slipping
planes are broken and
remade in succession.
12. SCREW DISLOCATIONS:
1.A dislocation in
the lattice
structure of a
crystal in which
the atoms are
arranged in a
HELICAL PATTERNS
that is normal to
the direction of
the stress .
2.It has no
extra planes
3.The defects
appears
through part
of the crystal
has been cut in
two, then
shifted down
on one side of
the cut.
14. TWIN BOUNDARY
The region between the pair
Of boundaries is called
“Twinned region”
one boundary is
restored by the
1
It is a special type of grain
boundary across which there is
MIRROR LATTICE.
Twins do not extend beyond a
grain boundary.
15. TWIN BOUNDARY cont…..
ANNEALINGTWINS
Twins which forms
during the process of
RECRYSTALLIZATION are
called “Annealing twins”
It is typically found in
metals that have
FCC crystal structure DEFORMATIONTWINS
Twins which forms during
the process of
PLASTIC DEFORMATION
are called “deformation
twins”
It is typically found in
metals that have
BCC and HCP crystal
