Thursday, 19 February 2015

9.3 Alloys

Physical properties of pure metals
■ Pure metal

Soft and not very strong.

Atoms of the same size arranged in a regular organised close packing arrangement.
■ Physical properties of pure metals:

Pure metals are soft and ductile because the layers of atoms can slide over each other easily when an external force is applied on them.

Most natural arrangement of atoms in pure metals are not perfect and may contain empty spaces in the structures.
When hammered or pressed, groups of metal atoms may glide into new position in these empty spaces. This makes metals malleable.
■ High melting and boiling point

Strong forces of attraction between metal atoms require high energy to overcome. Thus, most metals have high melting and boiling points.

■ Alloy

Mixture of a pure metal with small quantities of other metals.
■ Arrangement of atom in an alloy

In alloying process, a foreign metal is added to the molten pure metal.

The foreign atoms filling up the spaces between the atoms of the pure metal.

These foreign metal atoms disrupt the orderly arrangement of the metal atoms.

Thus the layers of metal atoms are prevented from sliding over each other easily.

This makes the metal harder, less malleable and less ductile.
Laboratory Activity 9.3.1 : Investigating the difference in hardness of an alloy and a pure metal
Purpose of making alloys
■ Purpose of making alloys

Increase the hardness of metals.

Prevent the corrosion of metals.

Improve beauty and lustre of metals.
■ Uses of alloys

The animation below shows the composition, properties and uses of some common alloys.

⇲ For exercise(objective and subjective), download for free on Android OS.

1 comment:

  1. In the construction industry, gears, pipes and other things are fabricated from alloy steels. By coupling additional elements to the carbon and iron based building metal you can strengthen it to withstand quite a bit more. Military aircraft use steel gears that are non-magnetic, high-quality, and corrosion-proof. Commercial steel buildings, roller skates, and tubing for boats and oil can be made using steel pipes.
    Alloys Well