This file for education only.

1. Chapter5
Metal and imperfections in solid

2. Chapter5
Metal and imperfection in solid
5.1 Solidification of Metals
- Solidification of Metals There are two steps:
❖The birth of (Nucleation): Which is the process of nuclei
formation in a molten metal.
❖Nuclei growth: Membranes form and form grains, with small
nuclei in the melted metal gradually increasing into one another
until the structures are grains. Like picture below.
1

3. Figure 5.1 Birth to preterm
2

4. 5.2 materials production in single crystal.
Most of the material has a masonry structure and is used in industrial
applications consisting of some polycrystalline structures with some single
crystals, such as some types of transistors, diodes, which are made of molten or
semi-conductive elements in the basic structure of the solids and high quality is
dissolved in a ceramic cup, which causes the chemical reaction to slow down and
the temperature to be maintained slightly above the melting point. Then, high-
quality and directional-based silicon casing will be deposited on the silicon that is
melted along with the treatment. The part of the surface of the magnesium used to
melt is dissolved into the liquid to remove the tension and produce the surface for
the liquid to continue to harden.
3

5. As the magnesium separates from the liquid in the ceramic cup, it will adhere and
grow on the molten gem, resulting in larger diameters of silicon, and this way we can
produce silicon bars of greater diameter up to 20 cm.
Figure 5.2 shows the silicon homogenization by the Czochralski process
4

6. 5.3 solid solution
Metal that we use in the current minority as metal pure or nearly pure often
contain other mixed use such as copper with high purity of 99.99% and a quick
navigation for work in electronics because of the ability to draw power from high
aluminum with high purity (called super pure aluminum) will be charged for
decoration because the metal surface shiny part Very often a metal mixed metal
alloy to make it more special quality Such as stronger, less developed and more
resistant to erosion. Alloys are a combination of metal and metal or metal with two
types wherein the structure of the alloy is not special, such as brass bearings which
are made up of two types of metal: 70% copper and 30% zinc,
5

7. Alloys are classified as solids or solids consisting of atoms of two or
more elements in the same structure, in two forms:
1) Substitutional solid solution)
The atoms of the two atoms: the solute atoms can be substituted for the
solvent atoms in the mass structure. The alkyl structures of this alloy are
unchanged but may be deformed, especially at different atomic sizes.
6

8. Figure 5.3 Substitutional solid solution
7

9. In the name of Hume Rothery, the one thing that can be replaced by
another atom must be:
1) The diameter of the two atoms must be no more than 15%.
2) The masonry structure of the two slaves should be the same.
3) Electronegativity must be very different, otherwise it would be a component.
4) Values ​​will be equal.
If the diameters of the two atoms of the constituents are different in solid
solvents, they will cause the crystal structure to collapse due to the lattice of the
atoms being able to shrink or shrink in limited quantities.
8

10. 5.3.2 solid solution of Sack cell.
Solids are solids formed by the atoms of the dissolved atoms
in the space between the atoms or the parent atoms between these
atoms. Soluble solids are formed only when the size of the atom is
larger than the size of the dissolved atom.
9

11. ❖Summary.
Most metals and alloys will melt and melt as semi-finished and
finished products. During the hardening of the metal the casting
process will form nuclei and grow into grains making the molten metal
more structured. Most industries require small grains where grains can
be found indirectly by ASTM grain size number n or directly derived
from average value of the grain size.
10

12. 5.4 imperfection of crystals
None of these are completely perfect but often have
structural defects, which result in different physical and
mechanical properties, such as the ability to form alloys at a low
temperature (cold formability), electrostatic charge of the
catalyst, and the rate of freezing.
The metal perfection can be divided into geometric and
physical properties, which are divided into three types:
11

13. 1) zero-dimension or point defects)
2) one-dimensional or linear defects
3) Two-dimensional point defects, which include the outer surface
and inner grains.
In addition three-dimensional macroscopic features on bulk
defects are formed by holes, cracks, and contaminants.
12

14. Figure 5.4
13

15. 5.4.1 Zero-dimension or point defects
1) Gaps are the most common imperfections caused by the loss of some atoms in the
structure, which often occur when metals dissolve by systemic disturbances during the
growth or redistribution of atoms in the structure of the atoms.
Figure 5.5 14

16. 2) Self-interstitial or interstitially
It is the imperfection of the point gem that arises because an
atom is inserted into the space between the atoms, which usually
does not occur because when they occur it can cause instability and
distortion. Point perfection can also occur in the structure of the
man-made cosmic system, which occurs in two ways:
2.1) Schottky imperfection is a point integrity caused by both
positive and negative ions emitted from the structure in order to
maintain the neutrality of the structure in the medium, resulting in 2
cations of positive and negative charge (cation-anion and divacancy).
15

17. 2.2) Frenkel imperfection is a perfect spot where the gap between the smaller
positively charged ions is not removed from the structure but engages in the gap
between the negative ions and the other positive ions.
5.4.2 one-dimensional or linear defects
Incompatibility can also be called: Dislocations, imperfections that cause
distortion of the gem, usually occur when the metal melts or where the plastic
deformation is present, which has the following two characteristics:
1) Edge dislocation is an extra half plane of atoms “inserted” into the
crystal lattice. Due to the edge dislocations metals possess high plasticity
characteristics: ductility and malleability.
16

18. Figure 5.6 shows the edge dislocation in the matrix where a linear defect occurs at
the top of the head frame with only a special half-plate of the atom.
17
Edge dislocation

19. 2) Screw dislocation: forms when one part of crystal lattice is shifted
(through shear) relative to the other crystal part. It is called screw as
atomic planes form a spiral surface around the dislocation line.
For quantitative characterization of a difference between a crystal
distorted by a dislocation and the perfect crystal the Burgers vector is used.
Figure 5.7 shows the occurrence of a screw dislocation with a slip or Burgers vector
parallel to the dislocation line 18

20. Figure 5.8 shows a composite dislocation occurring in the gem
19

21. 5.4.3 Two-dimension point defects
Surface or 2-dimensional imperfections include external surfaces such
as twins, low-angle boundaries, high-angle boundaries, twists, and stacking
faults. The facial imperfections are arranged differently, divided into 2 parts.
And looks as if one part is a shadow of another (When looking at the mirror)
Called: Twin boundaries
Figure 5.9 20

22. Twins are another example of 2-dimensional
imperfection, which refers to the area where the reflection of
a structure appears through a surface or horizon, it occurs
when the material undergoes a plastic deformation or
permanent deformation.
In addition, twin boundaries can be found during the
refinement process, whereby the atom itself will redefine
positions in the annealing twin structure, but this
phenomenon will only occur with FCC-style alloys.
21

23. 5.4.4 three-dimensional or volume imperfections.
imperfection volume or 3 dimension is occurring when a
group of imperfection point to by jolt to gather it will be happen or
pore in contrast on the other hand, a group of dilute atoms that may
merge into a 3-dimensional array. The size of the volume
imperfections may range from a few inches to several centimeters,
or sometimes larger, Such imperfections will significantly affect the
behavior and efficiency of the material.
22

24. Figure 5.10 three-dimensional or volume imperfections.
23

25. ❖Summary
Imperfections in the structure of the atoms are usually found in all kinds of
real-world materials, where such imperfections may occur in atomic or ionic gaps
or atomic positions that can be described in terms of atomic motion due to heat and
is considered to be imperfect in the equilibrium macro structure. Imperfections
dislocations (metallic imperfections) occur in the metallic structure of the metal
and are often multiplied by the hardening process, where the imperfections are not
imperfect and will increase the internal energy of the metal, The grain boundary is
imperfect on the surface of the metal, which results in a different orientation,
which ends in a solid state.
24

26. Other important imperfections that affect the
material integrity are: the low-angle boundaries,
High-angle boundaries, twists, imperfections
(stacking faults) and sediments.
25

27. ❖ Explanation of Stacking fault
In crystallography, a stacking fault is a type of defect which characterizes
the disordering of crystallographic planes. It is thus considered a planar defect
Figure 5.10: Comparison of fcc and hcp lattices, explaining the formation of sta
cking faults in close-packed crystals. 26

28. A stacking fault is a one or two-layer interruption in the stacking sequence of the
crystalline structure. These interruptions carry a certain stacking fault energy.
28

29. 29
Figure 5.1: imperfection of crystal structure

30. Point defects
The simplest point defects are as follows:
❖ Vacancy: missing atom at a certain crystal lattice position
❖ Interstitial impurity atom: extra impurity atom in an interstitial position
❖ Self-interstitial atom: extra atom in an interstitial position
❖ Substitution impurity atom: impurity atom, substituting an atom in
crystal lattice
❖ Frenkel defect: extra self-interstitial atom, responsible for the vacancy
nearby.
30