10. Aluminiumanditsalloys

Aluminium is the most abundant element in nature: about 7.5 per cent of the earth's crust consists of aluminium.

Aluminium is extracted from rock with a high alumina content. The most important sources are bauxite, kaolin, nepheline and alunite.

Bauxite is the principal source of aluminium. The less silica in a bauxite the higher quality of the aluminium ore. Kaolin clays are very abundant in nature but the extraction of aluminium from these ores presents diffi­culties due to the considerable amount of silica.

The most important properties of aluminium are its low specific gravity, high electrical and thermal conductivities, high ductility, and corrosion resistance in various media.

Pure aluminium has only few applications. It is used for the manufacture of electrical wire, chemical apparatus, household utensils and for coating other metals. Aluminium alloys are more widely used in industry. Wrought aluminium alloys have a high mechanical strength which in some cases approaches the strength of steel. Wrought aluminium alloys are further classified as non-heat-treatable and heat-treatable alloys. Wrought aluminium alloys also include complex alloys ofaluminium with copper, nickel, iron, silicon and other alloying elements. Complex wrought aluminium alloys of the duralumin (dural) type have found most extensive application in many industries.

1. Mark the sentences “True” or “False”:

1. Aluminium isn't the most abundant element in nature.

2. Aluminium is extracted from rock with a high alumina content.

3.The considerable amount of silica presents diffi­culties for the extraction of aluminium from ores.

4. One of the most important properties of aluminium is its high specific gravity.

5. Aluminium alloys are more widely used for the manufacture.

2. Match the beginnings of sentences to their endings:

1. The most important sources of aluminium are	A. for the manufacture.
2. Pure aluminium is used	B. bauxite, kaolin, nepheline and alunite.
3. Aluminium alloys are used	C. copper, nickel, and other elements.
4. Wrought aluminium alloys include	D. application in many industries.
5. Wrought aluminium alloys have found	E. in industry.

3. Match the terms with their definitions:

1. aluminium	A. a naturally occurring solid material from which a metal or valuable mineral can be extracted profitably
2. alloy	B. a light silvery-grey metal
3. ore	C. a hard, strong grey or bluish-grey alloy of iron with carbon and usually other elements, used as a structural and fabricating material
4. extraction	D. a metal made by combining two or more metallic elements, especially to give greater strength or resistance to corrosion
5. steel	E. the action of taking out something