TOPIC 1 : MATERIAL STRUCTURE & BINARY ALLOY JF302/ 1/ 1 1.0 MATERIAL STRUCTURE & BINARY ALLOY 1.1 Atom Is the elementary particles that make up all the materials either in the form of solid, gas or liquid. Atomic size is very small, however it has the weight and the properties of its own. The atom consists of three basic particles as shown below : Particle Charge Proton Positive Neutron Neutral Elektron Negative In terms of the charge, the atom is neutral because the proton has a charge opposite to the electrons. The nucleus consists of protons and neutrons. While electrons rotate around it. Arrangement of electrons in atoms is shown in Figure 1 Figure 1: Position of the electron, the atomic nuclei and orbital 1.2Elements A combination of two or more atoms of same type. It is in original condition. Example: the less relative metal such as gold and paltinium. Non-metals such as diamond, graphite, and sulfur. 1.3 Mixture A combination of two or more atoms of different types, but not chemically combined. 1.4 Compounds A combination of two or more different atoms chemically joined. Example: Iron + sulphide and heated, produce iron sulfide. Natural compounds are very stable because the particles are rigidly held therein. So it will not be easily knocked down. Eg: Sodium Chloride can be decomposed at a temperature of 800C. Bonding that occurs is called chemical bonds. Nucleus which consist of proton dan neutron Electron Shell / orbital 1 Orbital 2 Orbital 3
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TOPIC 1 : MATERIAL STRUCTURE & BINARY ALLOY JF302/ 1/
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1.0 MATERIAL STRUCTURE & BINARY ALLOY
1.1 Atom
Is the elementary particles that make up all the materials either in the form of solid, gas or
liquid. Atomic size is very small, however it has the weight and the properties of its own.
The atom consists of three basic particles as shown below :
Particle Charge
Proton Positive
Neutron Neutral
Elektron Negative
In terms of the charge, the atom is neutral because the proton has a charge opposite to the
electrons. The nucleus consists of protons and neutrons. While electrons rotate around it.
Arrangement of electrons in atoms is shown in Figure 1
Figure 1: Position of the electron, the atomic nuclei and orbital
1.2Elements
A combination of two or more atoms of same type. It is in original condition. Example:
the less relative metal such as gold and paltinium. Non-metals such as diamond, graphite,
and sulfur.
1.3 Mixture
A combination of two or more atoms of different types, but not chemically combined.
1.4 Compounds
A combination of two or more different atoms chemically joined. Example: Iron +
sulphide and heated, produce iron sulfide. Natural compounds are very stable because the
particles are rigidly held therein. So it will not be easily knocked down. Eg: Sodium
Chloride can be decomposed at a temperature of 800 C. Bonding that occurs is called
chemical bonds.
Nucleus which consist of
proton dan neutron
Electron
Shell / orbital 1
Orbital 2
Orbital 3
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1.4 Element Periodic Table
Consists of 109 elements. Vertical column in the named group. Sometimes called the
horizontal column. Periodic table has eight groups, from group I to VIII. Four groups
have special names, such as in Figure 1.3. This table has a middle block, known as the
transition elements.
Figure 1.3 : Element Periodic Table
N
7
Nitrogen
14
2:5
Atomic weight
Symbol
Name of element
Electron Configuration
Atomic number
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1.5The characteristic of Element Periodic Table
Chemical properties of an atom depends on the number of electrons in the outer shells of
atoms, called atomic valence . In this arrangement, the elements have the same number of
electrons in the outer shell will be included in the same group. This is why the elements
in the same group have similar chemical properties. Elements in group 1 had an electron
in the outer shell, the elements in group 2 has 2 electrons in the outer shell.
Each periodic with the same number of shells.
1.6 The Usage of Element Periodic Table
To facilitate the classification of an element. It also gives information about the elements,
especially the properties of the element as it is collected in order. Facilitate expect an
element that is still in the discovery and predicting the properties and usage. Easy to
analyze and understand a reaction between the elements.
1.7 Electron configuration (order of filling electrons in orbital)
Each shell can only be filled by a certain number of electrons only. If a shell has been
fully completed, other electrons to be filled into the next shell. Generally, the electrons
will occupy the shell closest to the nucleus prior to occupying other shell.
Fill the electrons in the shell closest to the nucleus first. This shell has the
lowest energy (e-max = 2n2). After that, the electrons are filled in the next
shell which is more powerful.
After the 18th elements, an exemption from this rule will apply. Where it
should be in the order which been determined. 1.8Crystal
Solids can be classified into solid crystalline and amorphous solids. Crystalline or
crystalline solid consisting of atoms arranged in a three-dimensional repetitive pattern or
uniform. Crystals composed of metallic and nonmetallic. Single crystals with unit cell is
composed of solid and uniform polycrystalline crystal consists of many single crystals in
Figure 1.4 below
Details of single crystal
(butiran hablur tunggal)
Grain boundries (sempadan
ira @ bijian)
Rajah 1.4 : Structure and grain boundries
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In the solidification process of atomic, liquid metal will react with each other and
organize their respective positions in a uniform and orderly form. The compilation of this
orderly process called space lattices. Crystals can be seen by using the X - Ray
defractometer while the grain can be seen clearly using metallurgical microscope after the
process of grinding, polishing, etching. Four types of crystal structures that are often
found is the simple cubic (simple cube), body-centered cubic (BCC), face-centered cubic
(FCC) and hexagonal closed pact (HCP) as in Figure 1.5.
Gambarajah fasa ialah peta sesuatu system dan ia menunjukkan fasa yang sepatutnya
wujud di bawah keadaan keseimbangan untuk sebarang gabungan rencaman dan suhu
tertentu. Gambarajah fasa digunakan secara meluas dan amat penting terutama untuk
memahami system logam dan aloi.
2.8.3 Composition (Komposisi)
Komposisi ialah peratus kandungan bahan-bahan tertentu yang sengaja atau tidak sengaja
dimasukkan ke dalam sesuatu bahan. Dengan kehadiran peratus komposisi bahan ini
boleh menyebabkan perubahan dalam fasa, sifat dan bentuk struktur mikro bahan.
2.8.4 Liquidus (Cecair)
Liquidus merujuk kepada garisan lintang yang memisahkan antara fasa cecair bahan
dengan fasa separa cecair bahan. Semasa proses pemejalan berlaku, zarah bahan yang
berada pada suhu lebur akan mula memejal apabila suhu diturunkan. Titik permulaan
proses pemejalan berlaku apabila melepasi garisan lintang liquidus.
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2.9 The process of solidification for pure metal and alloy according to the cooling
curve (Proses pemejalan Logam tulen dan aloi merujuk kepada Graf lengkung
Pendinginan)
1) Metal Cooling curve diagram (Graf lengkung pendinginan Logam Tulin)
Apabila logam disejukkan ke suhu beku, ia mengalami kesukaran untuk
membentuk hablur/nukleus.
Keadaan ini berlaku di antara 0.1 hingga 10°C (Kawasan B hingga C)
Apabila nukleus mula terhasil, suhu akan meningkat ke titik suhu beku (Thermal arrest) yang sebenar (D) dan suhu tidak dibebaskan lagi.
Apabila pembentukan hablur tamat (E) suhu akan terbebas semula. 2) Alloy Cooling Curve diagram (Graf lengkung pendinginan Aloi)
Apabila penyejukan berlaku, haba dibebaskan hingga ke suhu beku dan unit-unit sel mula terbentuk.
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Apabila sampai pada titik beku (Thermal arrest), haba tidak lagi dibebaskan kerana digunakan untuk pembentukan hablur-hablur hingga selesai.
Selepas itu haba kembali dibebaskan (Equilibrium Freezing Temperature)
2.9 The phase balance diagram, which comprises of a few cooling curves for solid solution (Gambarajah Keseimbangan Fasa, terhasil dari gabungan graf lengkung pendinginan Larutan Pepejal)
Sistem pancalogam atau aloi ini lebih mudah dipelajari dengan merujuk kepada gambarajah keseimbangan fasa atau gambarajah juzuk aloi tersebut. Rajah keseimbangan ini berdasarkan kepada suhu dan peratusan kandungan aloi yang boleh membantu memahami dan meramalkan apakah perubahan struktur aloi yang berlaku sewaktu pemanasan dan penyejukkan untuk pembekuan. Rajah ini juga penting sebagai panduan bagi proses rawatan haba dan memperbaiki sifat-sifat kimia bahan tersebut. Di dalam kebanyakkan aloi perduaan (binary alloy) iaitu campuran diantara dua jenis logam, juzuk-juzuknya boleh larut antara satu sama lain dalam keadaan cecair.
Berikut adalah graf lengkung pendinginan sebenar bagi aloi @ pancalogam:- Keadaan sebenar ini menunjukkan nisbah yang wujud di antara titik mula pemejalan (Liquidus point) dan titik tamat pemejalan (Solidus point) yang disebut “Freezing Range”.
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Sekiranya lengkung ini diplotkan sebanyak 6 graf, hasilnya dapat dilihat seperti di bawah :-
The construction of phase balance diagram (Mekanisma pewujudan rajah keseimbangan fasa)
Contoh penafsiran graf keseimbangan fasa:
1455
1083
t2
t1
t3
p
q r
m n
Larutan pepejal
Su
hu
(o C
)
100% Cu X% Ni 100
% % Ni
t1 – suhu pemejalan bermula
t3 – suhu pemejalan berakhir
t2 – cecair yang kerencaman m
berada dalam keadaan
keseimbangan dengan
larutan pepejal kerencaman.
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Rajah di atas menunjukkan suatu aloi yang mengandungi X % nikel akan memejal seperti
berikut :
i. Pada suhu t1, kerencaman cecair 1 akan berada dalam keadaan keseimbangan
dengan larutan pepejal kerencaman yang sepadan kepada titik p pada garisan
solidus (garisan pepejalan). Oleh itu hablur larutan pepejal pertama membentuk
terdiri dari kerencaman p.
ii. Apabila suhu turun maka kerencaman larutan pepejal berkecenderung untuk
berubah dengan cara resapan mengikut garisan pepejalan kepada titik q.
iii. Pada suhu t2, cecair yang kerencaman m berada dalam keadaan keseimbangan
dengan larutan pepejal kerencaman.
Proses pemejalan aloi ini akan selesai pada suhu t3 apabila titisan terakhir cecair
kerencaman n, memejal, membaiki kerencaman hablur larutan pepejal kepada r.
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EXERCISE
1. Atom consist of nucleus and ..................
A. Electron B. Proton C. Neutron D. Atomic number
2. Nukleus consist of............... and proton.
A. Neutron B. Atomic number C. Electron D. Proton
3. Atomic Number is a the total of ...............in an atom.
A. Proton B. Neutron C. Atomic number D. Electron
4. Atomic Mass Number is the total of the quantity of proton plus the quantity of...........
A. Elektron B. Proton C. Neutron D. Nombor atom
5. Atomic number of Ferum is 26, so the oleh itu Atomic Mass Number of Ferum is
..........
A. 26 B. 52 C. 78 D. 104
6. Atomic number of Magnesium ialah 12, so the number of orbital is ...........
A. 1 B. 2 C. 3 D. 4
7. The total number of electron at orbital no-3 not more than ...........
A. 6 B. 12 C. 18 D. 24
8. Atomic number of Aluminium is 13, so the quantity of elektron at the last orbital is
.............
A. 1 B. 2 C. 3 D. 4
9. One of the type of atomic bond is ............... A. mass B. Proton C. Elektron D. Metal
10. Solid solution consists of the substitutional type and...................
A. reverse B. return C. Interstitial D. Middleness