METALLURGY

METALLURGY

OF

OF

ALUMINUM

ALUMINUM

PROPERTIES

PROPERTIES



the lightest of the common metals

(except with Mg) with density = 2.7

g/cc (

1

/

3

the density of Cu).



soft and malleable at ordinary

temperature (becomes brittle when

heated to above 150

o

C).



silvery white in color



an amphoteric metal



good conductor of heat and electricity



an active metal but it does not corrode

OCCURENCE

OCCURENCE

Aluminum is the most abundant and the 3

rd

plentiful element on the earth’s crust.
The elemental form does not occur in
nature, its principal ore is bauxite. The
major sources of aluminum are:



bauxite, Al

2

O

3

.

H

2

O



cryolite, Na

3

AlF

6



corundum, Al

2

O

3



orthoclase, KalSi

3

O

8



beryl, Be

3

Al

2

Si

6

O

18

USES

USES



its chief use is in automobile and
aircraft construction.



kitchen utensils, aluminum foil and
beverage cans



high voltage transmission line



used as solid propellant for rockets



in the welding of iron and steel.

PREPARATION

PREPARATION



Aluminum is usually prepared from
bauxite.



Hall Process reduces bauxite to
aluminum.



The cell contains a series of carbon
(graphite) anodes.



The cathode is also made of carbon
and constitutes the lining inside the
cell.

HALL PROCESS

HALL PROCESS



The aluminum oxide from bauxite is melted with

cryolite to form 5% solution. The oxide dissociates as

follows:

Al

2

O

3

 2Al

+3

+ 3O

-2

 



The mixture is electrolyzed to produce aluminum and

oxygen gas:

Anode : 3 [2O

-2

- 4e

-

 O

2

]

Cathode : 4 [Al

+3

+ 3e

-

 Al]

 



 The overall reaction is:

2Al

2

O

3

 4Al + 3O

2

 



Oxygen gas reacts with the carbon anodes to form

monoxide, which escapes as a gas. The liquid aluminum

metal (m.p. 660.2

o

C) sinks to the bottom of the vessel

from which it can be drawn from time to time.