Industrial Materials Lectures.pptx

Introduction
. Heat Treatment
• Heat Treatment process is a series of operations
involving the Heating and Cooling of metals in the
solid state.
• Its purpose is to change a mechanical property or
combination of mechanical properties so that the metal
will be more useful, serviceable, and safe for definite
purpose.
• By heat treating, a metal can be made harder, stronger,
and more resistant to impact, heat treatment can also
make a metal softer and more ductile.

• No one heat-treating operation can produce all of these
characteristics. In fact, some properties are often
improved at the expense of others. In being hardened,
for example, a metal may become brittle.

The types of Heat Treatment:
1. Softening.
2. Hardening.

1. Annealing
• Annealing is the process for softening materials or to
bring about required changes in properties, such as
machinability, mechanical or electrical properties, or
dimensional stability.
• The annealing process consists of heating the steel to or
near the critical temperature (temperature at which
crystalline phase change occurs) to make it suitable for
fabrication.
• A material can be annealed by heating it to a specific
temperature and then letting the material slowly cool to
room temperature in an oven.

• When an annealed part is allowed to cool in the
furnace, it is called a "full anneal" heat treatment.

2. Normalizing
• It is a type of heat treatment applicable to ferrous
metals only.
• It differs from annealing in that the metal is heated to a
higher temperature and then removed from the furnace
for air cooling.
• The purpose of normalizing is to remove the internal
stresses induced by heat treating, welding, casting,
forging, forming, or machining.

• Normalizing is used in some plate mills, in the
production of large forgings such as railroad wheels
and axles, some bar products. This process is less
expensive than annealing.

3. Quenching or Hardening
• It is done to increase the strength and wear properties.
One of the pre-requisites for hardening is sufficient
carbon and alloy content.
• To harden by quenching, a metal (usually steel or cast
iron) must be heated into the austenitic crystal phase
and then quickly cooled.
• Depending on the alloy and other considerations (such
as concern for maximum hardness vs. cracking and
distortion), cooling may be done with forced air or
other gas (such as nitrogen), oil , polymer dissolved in
water, or brine.

• One drawback of using this method by itself is that the
metal becomes brittle. This treatment is therefore
typically followed by a tempering process which is
a heating process at another lower specific
temperature to stress relieve the material and
minimize the brittleness problem.

4. Case Hardening
• Case Hardening is the process of hardening the surface
of a metal, often a low carbon steel, by infusing
elements into the material's surface, forming a thin
layer of a harder alloy.
• Case hardening improves the wear resistance of
machine parts without affecting the tough interior of
the parts.

5. Austempering
• Austempering is heat treatment that is applied to
ferrous metals, most notably steel and ductile iron.
• In steel it produces a bainite microstructure whereas in
cast irons it produces a structure of acicular ferrite and
high carbon, stabilized austenite known as ausferrite.
• It is primarily used to improve mechanical properties
or reduce / eliminate distortion.

6. Tempering
• Tempering is carried out by preheating previously
quenched or normalized steel to a temperature below
the critical range, holding, and then cooling to obtain
the desired mechanical properties.
• Tempering is used to reduce the brittleness of quenched
steel.
• The temperature chosen for the tempering process
directly impacts the hardness of the work piece . The
higher the temperature in the tempering process, the
lower the hardness.

7. Surface Hardening
• Surface hardening, treatment of steel by heat or
mechanical means to increase the hardness of the outer
surface while the core remains relatively soft.
• Surface-hardened steel is also valued for its low and
superior flexibility in manufacturing.
• The oldest surface-hardening method is carburizing, in
which steel is placed at a high temperature for several
hours in a carbonaceous environment. The carbon
diffuses into the surface of the steel, rendering it harder.

• Another method of surface hardening, called nitriding,
utilizes nitrogen and heat. Cam shafts, fuel injection
pumps, and valve stems are typically hardened by this
process.
• Flame hardening and induction hardening, in which
high heat is applied for a short time (by gas flame or
high-frequency electric current, respectively) and then
the steel is immediately quenched, are used generally
for larger implements.

• Mechanical means of hardening the surface of steel
parts include peening, which is the hammering of the
heated surface, as by iron pellets shot onto the surface
or by air blasting, and cold-working, which consists of
rolling, hammering, or drawing at temperatures that
do not affect the composition of the steel.

8.MARTEMPERING(MARQUENCHING)
• To overcome the restrictions of conventional quenching
and tempering, Martempering process can be used.
• Martempering or marquenching permits the
transformation of Austenite to Martensite to take place
at the same time throughout the structure of the metal
part.
• Residual stresses developed during martempering are
lower than those developed during conventional
quenching.

• Martempering also reduces or eliminates susceptibility
to cracking.
• Another advantage of martempering in molten salt is
the control of surface carburizing or decarburizing.

9. Ausforming
• Ausforming also known as Low and High
temperature thermomechanical treatments is a method
used to increase the hardness and stubbornness of an
alloy by simultaneously tempering, rapid cooling,
deforming and quenching to change its shape and refine
the microstructure.

Fracture
:Simple fracture is the separation of a body into two or more pieces in
response to an imposed stress that is static (i.e. constant or slowly
changing with time) and at temperatures that are low relative to the
melting temperature of the material.
The applied stress may be tensile,compressive,shear or torsional.
The present discussion will be confined to fractures that result from
uniaxial tensile loads.
Any fracture process involves two steps :
i. Crack formation
ii. Propagation
For engineering materials, two fracture modes are possible
1.Ductile
2.Brittle

Ductile
Fracture:
Classification is based on the ability of a material
to experience plastic deformation.
Ductile materials typically exhibit substantial plastic
deformation with high energy absorption before
fracture.
ductility may be quantified in terms of
1. %EL = Final length - Initial Length x 100
Initial Length
2. % RA= Original area- final area x 100
original area

Cont…
Ductile fracture is characterized by extensive plastic
deformation in the vicinity of an advancing crack.
Ductile fracture is almost always preferred for two reasons.
1stbrittle fracture occurs suddenly and catastrophically without
any warning:
This is consequence of the spontaneous and rapid crack
propagation.
On the other hand, the ductile fracture, the presence of plastic
deformation gives warning that fracture is imminent, allowing
preventive measures to be taken.

Cont….
Second, more strain energy is required to induce
ductile fracture in as much as ductile materials are
generally tougher.
Ductile fracture surfaces will have their own
distinctive features on both microscopic and
macroscopic levels.
Below fig shows schematic representations for two
characteristics macroscopic fracture profiles.

Cont…
Fig (a) is found for extremely for softy metals such as pure gold and
lead at room temperature, an other metals, polymers, and inorganic
glasses at elevated temperature.
These highly ductile materials neck down to a point fracture, showing
virtually 100% reduction in area.

Stages of fracture:
The fracture process normally occurs in several stages given
below.

1st, after necking begins, in fig(b) small cavities on micro
voids, in the interior of the cross-section.
Next as deformation continues these micro voids in large,
come together, and coalesce to form an elliptical as shown in
fig ©. Which has long axis perpendicular to the stress
direction.
The crack continues to grow in a direction parallel to its major
axis by micro voids coalescence process in fig (d).
Finally fracture occurs by rapid propagation of a crack round
the outer parameter of the neck as in fig (e).
Shear deformation at an angle of 45 degree with tensile axis.

Brittle fracture:
Brittle fracture takes place without any appreciable
deformation, and by rapid crack propagation.
The direction of crack motion is very nearly perpendicular
to the direction of applied tensile stress and yields a
relatively flat fracture surface, as indicated in fig 8.1 ©.
Brittle fracture in amorphous materials such as ceramic
glasses, yields relatively shiny and smooth surface.
For most brittle crystalline materials cracks propagation
corresponds to the successive and repeated breaking of
atomic bonds along specific crystallographic planes.

Cont…
Such a process is termed cleavage.
This type of fracture is said to be transgranular(or
trans crystalline),because the fracture cracks pass
through the grains.
In some alloys crack propagation is along grain
boundaries, this fracture is termed as intergranular.

As History Tells Us
Stone Age and Bronze Age:
Humans have used metals for thousands of years.
Gold and silver, found as native metal, were used as
jewellery. These metals were known in the Stone Age but
gold and silver are too soft to be used as tools. The first
really useful metallic alloy to be discovered was bronze in
the Bronze Age. Bronze is not an element (like gold and
silver) but an alloy (metal mixture) of copper and tin.
Bronze was used extensively for tools and weapons.

As History Tells Us
Iron Age:
After the Bronze Age came the Iron Age.
People discovered that a high temperature coal
fire could be used for the extraction of iron from
iron ore. The discovery of electricity at the
beginning of the nineteenth century allowed the
extraction of the more reactive metals.
Aluminium has been extracted on a large scale
since about 1870.

Some Terms – Lets Have a Look
Minerals: A solid element or compound which
occurs naturally in the Earth's crust is called a
mineral.
Ore: A mineral from which metals can be extracted
profitably is called a metal ore. Profitable extraction
means that the cost of getting the metal out of the
ore is sufficiently less than the amount of money
made by selling the metal. So All Ores Are Minerals
But All Minerals Are Not Ores.
The most common metal ores are oxides and
sulphides. Metals are obtained from their ores by
reduction.

Be Aware!!
Metal ore deposits are a finite resource (there are
only a certain amount of them) and non-renewable
(once used, they are gone and will not be
replaced). Many metals are obtained today from
recycling (melting and refining) scrap metals.
Native Metals: Gold and platinum occur in the
Earth as native metal, which means that they are
found as the element, not the compound, and so do
not need to be reduced. Silver and copper may also
be found as native metal.

Occurrence of Iron
Iron is very reactive and is found in nature in form of
its oxides, carbonates and sulphates. The main
ores are:
i) Haematite (Fe2O3)
ii) Magnetite (Fe3O4)
iii) Iron Pyrites (FeS2)
o The main iron ore is Haematite (iron (III) oxide -
Fe2O3).
o The iron ore contains impurities, mainly silica
(silicon dioxide).
oSince iron is below carbon in the reactivity series,
iron in the ore is reduced to iron metal by heating
with carbon (coke).

Extraction of Iron
Step1: Concentration
The ore is crushed in crushers and is
broken to small pieces. It is concentrated with
gravity separation process in which it is
washed with water to remove clay, sand, etc.

Steps of Extraction
Step2: Calcination
The ore is then heated in absence of air
(calcined). This results in decomposition of carbonates
into oxides and then ferrous oxide is converted into
Ferric Oxide.
2
3
O 2 2 Fe2 CO 3
FeO CO
FeCO
4FeO

Steps of Extraction
Step2: Calcination
Step3: Smelting
The concentrated ore is mixed with
calculated quantity of coke, limestone and the
mixture is put in the Blast Furnace from top.

Blast Furnace
It is a tall cylindrical furnace
made of steel.
It is lined inside with fire
bricks.
It is narrow at the top and has
an arrangement for the
introduction of ore and outlet for
waste gases.
 Heated with help of Hot Gases.

Chemical Reactions
Following Chemical Reactions Take Place in a
Blast Furnace
i) Formation of Carbon Monoxide:
Near the bottom of the furnace, coke burns in air to
form Carbon Dioxide and a lot of heat is produced.
We get a temperature of about 1875 K.
This CO2 further reacts with more coke and is
reduced to CO.
C O2 CO 2 Heat
C CO 2 2CO

Chemical Reactions
ii) Reduction of Haematite to Iron:
In the upper part of the furnace, the temperature is
between 975K to 1075K. Here Haematite is
reduced to Iron by CO. This molten Iron is
collected at the bottom of the furnace.
2
2Fe 3CO
Fe 2O 3 3CO

Functions of Limestone
1. It acts as flux to remove sand from Haematite in form
of liquid Slag. In the middle of the furnace, the
temperature is about 1075-1275 K. Here Limestone
decomposes to produce calcium oxide (CaO) and
CO2.This CaO reacts with reacts with silica (sand)
present in the ore to form slag(CaSiO3).
2. Slag is lighter than molten iron so it floats over
molten iron and protects it from oxidising back into its
oxides.
2 3
2
3
CaCO heat CaO CO
CaO SiO CaSiO

• Iron(III) oxide, coke, limestone and air are
used in the extraction of iron.
• The iron is obtained by the reduction of
iron(III) oxide with carbon monoxide.
• Most impurities are removed by reaction
with calcium oxide (from limestone) to
produce slag.

Commercial Forms of Iron
There are three major commercial forms of Iron.
They differ in their carbon content.
1. Cast Iron (or Pig Iron)
It contains 2-5% Carbon along with traces of other
impurities like Sulphur, Phosphorus, Manganese
etc.
2. Wrought Iron
It is the purest form of Iron and contains carbon to
the extent of 0.25%
3. Steel
It contains 0.5 to 1.5 % of carbon along with varying
amount of other elements.

Testing Zone..
Match the following:
a) Haematite
b) Calcination
c) Smelting
d) Slag
e) Lime Stone
a) Extraction of Iron
b) Ore of Iron
c) CaSiO3
d) Acts as Flux
e) Type of Iron
f) Heating in absence of air.

Testing Zone..
Mark True of False
1. Metals can be extracted profitably from ores.
2. All minerals are ores.
3. Chief ore of Iron is Iron Pyrites.
4. Iron is reduced with the help of Coke.
5. Slag is formed by reaction between CaCO3 and SiO2

Testing Zone..
Mark True of False
1. Metals can be extracted profitably from ores. (True)
2. All minerals are ores. (False)
3. Chief ore of Iron is Iron Pyrites. (False)
4. Iron is reduced with the help of Coke. (True)
5. Slag is formed by reaction between CaCO3 and SiO2.
(False)

Testing Zone..
Choose the right Answer out of
The given choices:
Ques1: The actual reducing agent in Blast Furnace is:
A) Coke
B) Carbon Dioxide
C) Carbon Monoxide
D) Iron

Testing Zone..
The given choices:
Ques2: The formula for Haematiteis:
A) FeO
B) FeO2
C) Fe2O3
D) Fe3O4

Testing Zone..
The given choices:
Ques3: Which is the purest form of Iron?
A) Cast Iron
B) Wrought Iron
C) Pig Iron
D) Steel

Do it Yourself
Q 1: Name three ores of Iron
Q 2: Write the chemical reactions taking place in a blast
furnace during extraction of Iron
Q3: What are three major types of Iron. How do they
differ from each other?
Q4: Draw a neat labelled diagram of Blast Furnace.

Exercise Time:
The Conditions in the Blast Furnace
1. What is the role of coke in the blast furnace?
It acts as a reducing agent
2. What is the role of limestone in the blast furnace?
Limestone helps to remove acidic impurities
3. Which ore of iron is commonly used in the blast furnace?
Haematite
4. Why is it called a blast furnace?
Because hot air is ‘blasted into the furnace’
5. What do we call the layer of impurities that forms at the base of
the blast furnace above the liquid iron?
Slag

Exercise:
1. Which compound does haematite mainly consist of?
Iron (III) oxide
2. What is the chemical formula of this compound?
Fe2O3

Exercise
1. Limestone is added to the blast furnace to remove acidic
impurities. What is the name and chemical formula of the
compound that limestone mainly consists of?
Calcium carbonate - CaCO3
2. In the blast furnace this compound undergoes thermal
decomposition. Write a word equation for this reaction.
Calcium carbonate  calcium oxide + carbon dioxide
3. What is the chemical equation for this reaction?
CaCO3 (s)  CaO (s)+ CO2 (g)
4. Calcium oxide reacts with the impurity silicon dioxide. Write the
chemical equation for this chemical reaction.
CaO (s) + SiO2 (s) CaSiO3 (l)

Questions :
1 a) Why is steel more suitable than iron in most uses ?
Iron is too malleable for most uses as the orderly layers of
atoms can slide over each other easily.
Steel is an alloy consisting of different sized atoms, which
disrupts the orderly arrangement of atoms, preventing the
layers from sliding over each other easily. Hence, steel is
harder and stronger for most uses.
b) Why is stainless steel popularly used for making cutlery ?
Stainless steel is corrosion resistant and does not rust.

1c)Why is recycling aluminium easier
than recycling scrap
iron?
Aluminium metal is very resistant to
corrosion. This is because aluminium reacts with
oxygen in the air to form a protective layer of
aluminium oxide. Iron has poor resistance to
corrosion and corrodes easily when exposed to air
and water. It Hence it is difficult to recycle.

ALUMINUM
PROPERTIES, USES,
EXTRACTION PROCESS, ALUMINUM ALLOYS

HIGHLIGHTS 
History
Ores
Extraction Methods
Properties
Alloys
Applications Pure Al Paste

BASIC
INFORMATION :
 Atomic number ?
 Electronic configuration?
 Density ?
 Atomic mass?
 Melting point?
 Boiling point ?
13
[Ne]3s23p1
2.7 g/cm3
26.9g
660∘C
2519∘C

HISTORY
 Alum?
is hydrated double sulphate salt of Al
 Commander Archelaus discovered that wood was
practically flame resistant if it was treated using an alum
solution.
 Scientist suspected an unknown metal in alum as
early as 1787.
40 years
Extraction Al

Humphry Davy : that aluminium could be
produced by electrolytic reduction from
alumina (aluminium oxide).
Hans Christian Oersted (Denmark) :
Was successful in extracting but produced an aluminium
alloy rather than pure aluminium.
Friedrich Woehler [German] :
continued Hans Christian’s work.
1808
1825
1827
1846 Friedrich created small balls of
solidified molten aluminium (globules)
1856 Henri-Etienne Sainte-Claire Deville[French] :
industrial applications. [DEVILLE PROCESS]
1856-1890
200 tonnes
of Al were produced in 36 years

BUT……
o Chou-Chu
o general of ancient China during the third century.
o Upon digging his tomb, historians found a piece of jewellery.
85% of the material of the jewellery was actually aluminium

INTRODUCTI
ON
 Aluminium is found in many rock minerals, usually
combined with silicon and oxygen in compounds called
Alumino silicates. Example: Kayanite (Al₂O(SIO₄)),
Topaz (Al₂O(SIO₄)(OH,F)₂), Kaolinite (Al₂Si₂O₃(OH)₄)
etc.
 Under certain types of tropical soil weathering these
alumina-silicate compounds are separated into layers
of hydrated iron oxide, hydrated alumina and silica.
Example: Al(OH)₃, Al₂O₃.3H₂O etc.
 When such deposits are rich in alumina, this comprise
the mineral bauxite. Bauxite is a mixture of gibbsite
(Al(OH)₃), boehmite (AlO(OH)) and diaspore
(AlO(OH)); and has a general formula of Al₂O₃.x2H₂O

ALUMINUM ORES
 There are a large number of minerals and rocks containing
aluminum; however, only a few of them can be used for extracting
metallic aluminum.
 Bauxites are the most widely used raw materials for aluminum.
 Initially a semifinished product, alumina (A12O3) is extracted from
the ores, and the metallic aluminum is produced electrolytically
from the alumina.
 Nepheline-syenites as well as nepheline-apatites are also used as
aluminum ores. These minerals are simultaneously used as a
source of phosphates.
 Other minerals which can be used as a source of aluminum
include alunites, leucitic lavas (the mineral leucite), labradorites,
anorthosites, and high-alumina clays and kaolins.

BAUXITE
 Bauxite is the most important aluminium ore. It consists
largely of the minerals gibbsite Al(OH)3, boehmite γ-
AlO(OH), and diaspore α-AlO(OH), together with the iron
oxides goethite and hematite.
 Bauxite does not have a specific composition. It is a
mixture of hydrous aluminum oxides, aluminum
hydroxides, clay minerals, and insoluble materials such as
quartz, hematite, magnetite, siderite, and goethite.
 Bauxite is typically a soft (H:1-3), white to gray to reddish
brown material with a pisolitic structure, earthy luster and
a low specific gravity (SG: 2.0-2.5).
 Bayer’s Process is the main process for the production
of bauxite.

RAW MATERIAL WITH USES FOR THE
EXTRACTION OF ALUMINIUM
RAW MATERIAL USE
Alumina Source of Aluminium
Crude Oil Making Coke
Coal Making Pitch
Coke, Pitch Electrode Manufacture
Cryolite (Na₃AlF₆) Dissolving Alumina at 970⁰C
(synthetically produced)
Electricity Reduction of Alumina to Aluminium

EXTRACTION PROCESS
1.DEVILLE PROCESS
2.SERPECK’S PROCESS
3.HALL-HEROULT PROCESS
4.BAYERS PROCESS

1.DEVILLE
PROCESS
 first industrial process.
 based on the extraction of alumina with sodium carbonate.
Calcination of the bauxite at
1200 °C with sodium
carbonate and coke.
The alumina is converted in
sodium aluminate. Iron oxide
remains unchanged and silica
forms a polysilicate.

sodium hydroxide solution is
added, which dissolves the
sodium aluminate, leaving the
impurities as a solid residue.
The solution is filtered off; carbon
dioxide is bubbled through the
solution, causing aluminium
hydroxide to precipitate, leaving a
solution of sodium carbonate
The latter can be recovered and
reused in the first stage. The
aluminium hydroxide is calcined
to produce alumina.

2.SERPECK’S
PROCESS
 This process is used for the purification of bauxite ore containingsilica
(SiO2) as the main impurity.
 The powdered ore is mixed with coke and the mixture is heated at
about 1800°C in the presence of Nitrogen gas, when aluminiumnitride
is formed.
Al2O3. 2H2O + 3C + N2 → 2AI N + 3CO+ 2H2O
 Aluminium nitride thus obtained is hydrolysed with water to geta
precipitate ofAl(OH)3.
2Al N + 6H2O → 2NH3 +Al(OH)3
 The precipitate of Al (OH)3 is filtered, washed and dried. The silica presentas
impurity in bauxite is reduced to silicon which being volatile at high
temperature. is removed easily.
SiO2 + 2C → Si + 2CO

3.HALL-HÉROULT
PROCESS
 Aluminium's development changed with the discovery of
a more cost-efficient electrolytic production method in
1886.
 It was developed by Paul Héroult, a French engineer, and
Charles Hall, an American student, independently and at
the same time.
 The method involved the reduction of molten aluminium
oxide in cryolite.
 The process demonstrated excellent results, but required
an enormous amount of electric power.

4.BAYER’S
PROCESS
STEP-1: Purification of bauxite - This is a two-step
process called Bayer's process:
a)First, we dissolve bauxite in aqueous sodium
hydroxide(NaOH) by digestion. Bauxite with higher
hydroxide contents (Al(OH)3) are treated at 120-140° C
with dilute(3M) NaOH and bauxite with higher oxide
content('AlOOH') is treated at a higher temperature(200-
250° C) and a higher pressure (35 atm) with 5-7M
NaOH.
b)The insoluble impurities are separated by filtration.
Al(OH)3 is precipitated by carbon dioxide and ignited to
~1200° C to obtain Al2 O3.

STEP-2: Purified bauxite is then dissolved in
cryolite(5-7% CaF2 , 5-7% AlF3, 2-8% Al2 O3) and
electrolyzed at 950° C in a carbon lined steel cathode
with hard carbon rods as the anode. Li2 CO3 is used to (i)
lower the melting point of the electrolyte (ii) permit
larger current flow and (iii) reduce fluorine emission.
 The resulting reactions are produced:
Al2 O3 → 2Al3++ 3O–
 At Cathode (positive electrode where reduction occurs
by gain of electrons) : 2 Al3++ 6e- → 2Al
 At Anode (negative electrode where oxidation occurs by
loss of electrons): 3O-- - 6e- →3O

ALLOYS OF ALUMINIUM
 Aluminium alloy Aluminium (Al) is the
predominant metal.
 The typical alloying elements are copper,
magnesium, manganese, silicon, tin and zinc.
 There are two principal classifications, namely
casting alloys and wrought alloys, both of which are
further subdivided into the categories heat -
treatable and non-heat-treatable.
 The most important cast aluminium alloy system is
Al–Si, where the high levels of silicon (4.0–13%)
contribute to give good casting characteristics.

ALLOYS OF ALUMINIUM AND IT’S
COMPOSITION
Alloy Name Al (%) Cu (%) Mn (%) Mg (%) Zn (%)
Duralumin 95 4 0.5 0.5 -
Magnalium 70-90 - - 30.10 -
Elektron 9-10 - 0.5 87-86 3.5

ALUMINIUM ALLOYS WITH THEIR USES
Major alloy
element
Content Product Some typical
uses
Copper Up to 4.5% Sheet
Extrusions
Castings
High strength
aircraft parts
Manganese 1.2% Sheet Sheetmetal
work,pots etc.
Silicon Up to 13% Castings Motor parts etc.
Magnesium and
Silicon
0.7% Mg, 0.4%
Si
Sheet
Extrusions
Architectural
extrusions
Magnesium Up to 5% Sheet Marine,
boats etc.
Zinc,
Magnesium and
Copper
5.8% Zn, 2.5%
Mg,
1.4% Cu
Sheet
Extrusions
High strength
aircraft

PROPERTIES OF
ALUMINIUM
 It has low density, is non-toxic, has a high thermal
conductivity, has excellent corrosion resistance and can
be easily cast, machined and formed.
 It is the second most malleable metal and the sixth most
ductile.
 It is cheaper than copper and weight for weight is almost
twice as good a conductor.
 It is often used as an alloy because aluminium itself is
not particularly strong.

 These properties lead to a variety of specialised uses.
1.Lightness:- Use in aerospace and transport industries, as
its lightness enables a greater volume of metal to be used,
thus giving greater rigidity. Also used in pistons,
connecting rods, etc. to give better balance, reduced
friction and lower bearing loads.
2.Specific Strength: It is known as the strength to weight
ratio of a material. Aluminium alloys have higher specific
strength value (12 – 125kNm/Kg) than cast iron and steel.
3.Electrical conductivity: Used extensively for electrical
conductors, especially in overhead Cables.

4.Thermal conductivity: Extensive usage in heat
exchangers, cooking utensils, pistons, etc.
5.Corrosion resistance: This is made use of in
chemical plant, food industry packaging, building
and marine applications. Aluminum paint is widely
used. The oxide film can be thickened by anodizing,
and the film can be dyed in a wide range of colors.
This is done by making the article the anode of a
direct current electrolysis cell using an electrolyte
solution of approximately 15% sulfuric acid.
2Al + 3H₂O→ Al₂O₃+ 6H₊ + 6e

6.Linear expansion: Compared with other metals,
aluminium has a relatively large coefficient of
linear expansion. This has to be taken into account
in some designs.
7.Non-magnetic material: Aluminium is a non-
magnetic material. To avoid interference of
magnetic fields aluminium is often used in magnet
X-ray devices.
8. Machining : Aluminium is easily worked using
most machining methods – milling, drilling,
cutting, punching, bending, etc. Furthermore, the
energy input during machining is low.

ADVANTAGES
 Aluminum has three main advantages when
compared with other metals.
1. It has a low density, about one third that of iron
and copper.
2. Although it reacts rapidly with the oxygen in air, it
forms a thin tough and impervious oxide layer
which resists further oxidation. This removes the
need for surface protection coatings such as those
required with other metals, in particular with iron.
3. Aluminum has a high corrosion resistance because
of the tough oxide film always present on the
surface of aluminum in the presence of air, water
vapor, etc., and it has a strong affinity for oxygen.

DISADVANTAGES
 The disadvantages of aluminium are as follows:
1. Aluminium can’t be used in such areas where
heavy loads are required. Due to its ductile nature,
it cannot take same stress like other elements, as
in steel.
2. Aluminium doesn’t give or bend as much as steel
which means that it’s more prone to breaking out
right. It also doesn’t absorb vibrations as good as
steel, which can be good or bad depending on the
situation.

ALUMINUM IS USED IN A HUGE VARIETY OF
PRODUCTS INCLUDING CANS, FOILS, KITCHEN
UTENSILS, WINDOW FRAMES, BEER KEGS AND
AERO PLANE PARTS.

ALUMINUM IS A GOOD ELECTRICAL CONDUCTOR
AND IS OFTEN USED IN ELECTRICAL TRANSMISSION
LINES.

WHEN EVAPORATED IN A VACUUM, ALUMINUM FORMS A
COATING FOR BOTH LIGHT AND
HIGHLY REFLECTIVE
HEAT. IT DOES NOT DETERIORATE,
COATING WOULD. THESE ALUMINUM
LIKE A
COATINGS
SILVER
HAVE
MANY USES, INCLUDING TELESCOPE MIRRORS,
DECORATIVE PAPER, PACKAGES AND TOYS.

BIOLOGICAL ROLE OF
ALUMINUM
 Aluminium has no known biological role. Our bodies
absorb only a small amount of the aluminium we take in
with our food.
 Cooking in aluminium pans does not greatly increase the
amount in our diet
 Aluminium can accumulate in the body, and a link with
Alzheimer’s disease (senile dementia) has been
suggested but not proven.

Industrial Materials Lectures.pptx

Industrial Materials Lectures.pptx

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