10 Aluminium and its alloys

10.1 Text 10

Next to oxygen, aluminium is the most abundant element in nature: about 7.45 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 its quality as an 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 present.

The most important properties of aluminium are its low specific gravity (2.7), 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 of aluminium with copper, nickel, iron, silicon and other alloying elements. Complex wrought aluminium alloys of the duralumin (dural) type and certain others have found most extensive application in many industries.

Several grades of duralumin are available in Russia. They are identified by the Russian letter Д fol­lowed by a figure indicating the number of the alloy in the series. Duralumin, grade Д-1 can be obtained in the form of sheets, bar stock and tubing; grades Д-6 and Д-16 аre usually produced in the form of bars, and grade Д-ЗП is made as wire for rivets.

10.2 Activities

Activity 1. Match the terms with their definitions

1 oxygen	A- existing or available in large quantities; plentiful
2 abundant	B- the chemical element of atomic number 13, a light silvery-grey metal.
3 gravity	C- a tool, container, or other article, especially for household use
4 aluminium	D- the force that attracts a body towards the centre of the earth, or towards any other physical body having mass
5 utensil	E- a colourless, odourless reactive gas, the chemical element of atomic number 8 and the life-supporting component of the air.

Activity 2. Mark the sentences “True” or “False”

1) Aluminium is extracted from rock with a high alumina content.

2) Duralumin, grade Д-1 can be obtained only in the form of sheets.

3) Next to oxygen, aluminium is the most abundant element in nature: about 5.45 per cent of the earth's crust consists of aluminium.

4) Pure aluminium has only few applications.

5) Kaolin clays are very abundant in nature and the extraction of aluminium from these ores presents no diffi­culties due to the considerable amount of silica present

Activity 3. Match the beginnings of sentences to their endings

1 The less silica in a bauxite	A- the higher its quality as an aluminium ore.
2 Wrought aluminium alloys also include complex alloys of aluminium with	B- the manufacture of electrical wire, chemical apparatus, household utensils and for coating other metals.
3 Next to oxygen, aluminium is the most abundant element in nature:	C- which in some cases approaches the strength of steel.
4 Pure aluminium has only few applications; it is used for	D- about 7.45 per cent of the earth's crust consists of aluminium.
5 Wrought aluminium alloys have a high mechanical strength	E- copper, nickel, iron, silicon and other alloying elements.

Activity 4. Answer the following questions

1) How often is aluminium occurred in the earth's crust?

2) What are the most important sources by aluminium extraction?

3) What are the most important properties of aluminium?

4) Where is pure aluminium used?

5) What do you know about aluminium alloys?

Activity 5. Explain the terms using

Earth’s crust, specific gravity, thermal conductivity, ductility, coating

Activity 6. Translate the words and word combinations

Next to oxygen, the most abundant element in nature, presents diffi­culties due to,

few applications, approaches the strength of steel, wrought aluminium alloys, non heat-treatable, alloying elements, they are identified by, can be obtained in the form of sheets

Activity 7. Find more information about aluminium and its alloys and discuss it