SUBMITTED BY: VARUN GULIA 12MEU089

ALUMINIUM

INTRODUCTION

Aluminium  is a chemical element with symbol  Al and atomic number 13.

Aluminium is the third most abundant element (after oxygen and silicon), and the most abundant metal in the Earth's crust.

It is a soft, nonmagnetic, ductile metal.Insoluble in water and alcohol.High electrical and thermal conductivity.

CHARACTERISTICS

Aluminium is a relatively soft, durable, lightweight.

Appearance ranges from silver to dull grey (depends on surface roughness).

 Yield strength of pure aluminium is 7–11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa.

Melting point: 660 °CBoiling point: 2500 °CDensity: 2.70 g/cm³

CORROSION RESISTANCE

When the surface of aluminium metal is exposed to air, a protective oxide coating forms almost instantaneously.

If the oxide becomes scratched and aluminium metal exposed, more oxide is formed and the protected layer renewed.

This oxide layer is corrosion resistant.This oxide layer is one of the main reasons

for aluminium good corrosion properties. The layer is stable in the general pH range 4 – 9.

STRENGTH

Aluminium alloys commonly have tensile strengths of between 70 and 700 MPa.

Aluminium does not become brittle at low temperatures.

At high temperatures, aluminium’s strength decreases.

The low density of aluminium does not affect its strength.

CONDUCTIVITY

Aluminium is an excellent conductor of heat and electricity.

Aluminium conductor weighs approximately half as much as a copper conductor having the same conductivity.

Resistivity: 2,82×10−8 Ωm Thermal Conductivity : 202.4 W/mK Commonly used material in power

transmission lines.

REFLECTIVITY

Aluminium is a good reflector of both visible light and heat.

Aluminium serves as a good reflector (approximately 92%) of visible light and an excellent reflector (as much as 98%) infrared radiation.

Aluminium is extremely reflective, when polished  and that together with its low weight, makes it an ideal material for reflectors ,for example, light fittings or rescue blankets.

DUCTILITY & MALLEABILITY

High Ductility & Malleability.Large coefficient of linear expansion.Aluminium is the 2nd most malleable and 6th

most ductile metal.

MACHININGAluminium is easily worked using most

machining methods – milling, drilling, cutting, punching, bending, etc. Furthermore, the energy input during machining is low.

FORMABILITY

With the metal either hot or cold, this property is also exploited in the rolling of strips and foils, as well as in bending and other forming operations.

IMPERMEABLE AND ODOURLESSAluminium foil, even when it is rolled to only

0.007 mm thickness, is still completely impermeable.

Non-ToxicReleases no aroma or taste substances which

makes it ideal for packaging sensitive products such as food or pharmaceuticals.

ISOTOPES

22 known isotopes from 21Al to 42Al.4 isomersOnly 27Al is stable26Al is a radioactive isotope27Al has a natural abundance of 99.9+ %Other than 26Al, all radioisotopes have half-lives

under 7 minutesAluminium isotopes have found practical

application in dating marine sediments, manganese nodules, glacial ice.

OCCURRENCE

Aluminium is highly reactive and does not occur in the free state.

It is widely distributed and it is third in abundance on earth.

Aluminium has three principal ores Gibbsite or Hydrargillite, Al2O3.3H2O, Bauxite, Al2O3.2H2O, Diaspore, Al2O3.H2O, and Cryolite, AlF3.3HF.

Aluminium also occurs in the form of its Aluminium Oxide, Al2O3, in the semiprecious stones.

EXTRACTION

In a two-stage process the metal is extracted from the bauxite ore under pressure and heat using the called Bayer process.

The aluminium hydroxide is then heated to produce aluminium oxide (alumina).

 the second process is the electrolysis of alumina. In this process alumina is dissolved in molten

cryolite and split into molten Al and O2 by passing an electric current.

From two tons of aluminium oxide thus one ton of primary metal is extracted.

BAYER’s PROCESS

Convert Bauxite to Alumina.Crush and Grind: The ore is then fed into

large grinding mills and mixed with a caustic soda solution (sodium hydroxide) at high temperature and pressure.

Digesters: The slurry is pumped to a digester where the chemical reaction to dissolve the alumina takes place.

Flash Cooling: The slurry is pumped into a series of flash tanks to reduce the pressure and heat.

Settlers: Settling is achieved primarily by using gravity, although some chemicals are added to aid the process.

Precipitation: The clear sodium aluminate from the settling and filtering operation is pumped into precipitators.

Calcination : Calcination is a heating process to remove the chemically combined water from the alumina hydrate.

Al2O3 + 2 NaOH → 2 NaAlO2 + H2O2 NaAlO2 + CO2 → 2 Al(OH)3 + Na2CO3 + H2O2 H2O + NaAlO2 → Al(OH)3 + NaOH 2 Al(OH)3 → Al2O3 + 3 H2O

HALL-HEROULT PROCESS

Convert Alumina to Aluminium.The aluminium oxide is mixed with cryolite

(made of sodium fluoride and aluminium fluoride) and then heated to about 980 °C to melt the solids.

The molten mixture is then electrolysed with a very large current.

Aluminium ions are reduced to form aluminium metal (at the cathode).

Oxygen gas is formed at the anode.

ALUMINIUM ALLOY’s

Aluminum alloys can be can be classified as

Wrought alloys Cast alloys

Each of these alloys can be further classified as

Non Heat treatable alloys Heat treatable alloys

WROUGHT ALLOY

 Each alloy is given a four-digit number, where the first digit indicates the major alloying element.

There are 7 series of Wrought alloy

1000 series are pure Al with a min 99% aluminium content by weight and can be work hardened.

2000 series are alloyed with Cu, can be hardened to strengths comparable to steel.

3000 series are alloyed with Manganese.4000 series are alloyed with silicon. They are also

known as silumin.5000 series are alloyed with Magnesium.6000 series are alloyed with magnesium and

silicon. They are easy to machine, are weldable.7000 series are alloyed with zinc.

CAST ALLOYS

Cast aluminium alloys are cost-effective products.

Low melting pointHave lower tensile strengths than wrought

alloysMost important cast aluminium alloy system

is Al–SiThere are 9 series of Cast Al Alloys:

MAJOR ALLOYING ELEMENTS

USES OF ALUMINIUM

TRANSPORTAluminum alloys are widely used for aeronautical

applications because of high strength weight ratio.

Aluminium-Scandium alloys are used in Aerospace industries.

In automobiles for reducing weight of the vehicle thus reducing fuel consumption.

In trucks and buses (sheet and plate for bodies)In Cars(engine blocks, cylinder heads,body

panels)

PACKAGING

Aluminium is used in the form of alloy sheet for beverage can bodies and tops.

As foil for household and commercial wrap, and in manufactured packaging products such as cartons for fruit juice and packaging for pharmaceuticals.

1000 series alloys as foil for food wrapping.

In construction, aluminium is used in sheet products for roofing and wall cladding, in extrusions for windows and doors, and in castings for builders' hardware.

In the electrical sector, aluminium is used in the form of wire, normally reinforced with steel to form cables.

House hold and consumer items such as utensils

RECYCLING

Aluminium is theoretically 100% recyclable without any loss of its natural qualities.

Recycling involves melting the scrap, a process that requires only 5% of the energy used to produce aluminium from ore.

Recycled aluminium is known as secondary aluminium, but maintains the same physical properties as primary aluminium.

ALUMINIUM LIFE CYCLE

Aluminium is the perfect ‘eco-metal’. Very little Al is lost in the remelting process. Increased recovery, dismantling and sorting of spent products has led to even greater recycling of aluminium.

REFERENCE

sam.davyson.com/as/physics/aluminiumriotintoalcan.com/ENG/ourproducts/

1542_aluminium_and_its_uses.asplen.wikipedia.org

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