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FIND OUT MORE. Circuits 184–185 • Elements 160–161 • First Metalworkers 367

An alloy is a mixture of metals, or of metals and other

substances. Mixing metals and other elements in alloys

can improve their properties. The alloy bronze is a

mixture of the metals copper and tin. It is resistant

to water corrosion and is used in outdoor structures.

NAME MAIN CONSTITUENTS USES

Brass copper, zinc musical instruments,

decorative items

Bronze copper, tin statues, bearings, coins

Cupronickel copper, nickel coins

Duralumin aluminium, copper, aircraft, bicycles

magnesium, manganese

Nichrome nickel, chromium electrical heating elements

Steel iron, carbon construction, tools,

vehicles

Stainless steel iron, chromium, carbon kitchen fittings,

cutlery, surgical equipment

Solder lead, tin joining metals

WHAT IS FLUX?

Flux is any substance that stops a metal oxidising

(combining with oxygen), such as salt. Most metals

oxidise in air – the process is speeded up with heat.

When a plumber joins a copper pipe with solder, he

coats the surface with flux. Flux stops the copper

oxidising. If the copper made an oxide, the solder

would not stick, and the pipes could not be joined.

DO ALLOYS MELT EASILY?

The different sizes of atoms in an alloy make their

arrangement less regular than a pure metal. This

makes the bonds between the atoms weaker, and

lowers the melting point. Alloys that melt easily,

such as. SOLDER, have important uses.

ARE ALLOYS STRONGER THAN PURE METALS?

A pure metal has identical atoms arranged in regular

layers. The layers slide over each other easily. Alloys

are harder and stronger because the different sized

atoms of the mixed metals make the atomic layers

less regular, so they cannot slide as easily.

WHO FIRST USED ALLOYS?

About 6,000 years ago, early peoples made the alloy

bronze by roasting together copper and tin ores

(minerals). Bronze is stronger and longer-lasting than

pure copper. This period in history when bronze was

the main material used is called the Bronze Age.

Lead is a heavy, soft metal, and melts at a

low temperature, 328°C (622°F). By adding

tin to make the alloy solder, the melting

point is lowered further.

4 STEEL ALLOY

The Atomium in Brussels,

Belgium, is built from steel

girders, which give it strength.

Steel is a mixture of iron and

carbon. The Atomium is covered

in aluminium, which protects it

from the weather. The nine

spheres are arranged like the

atoms in iron. There is a science

museum inside the spheres.

Alloys

METAL TOOLS 3

The metal for a good tool

must be strong enough to

take blows, and hard

enough to sharpen to a

fine cutting edge. Modern

tools are still made from

iron, alloyed with carbon.

SOLDER

HEATING SOLDER 1

Solder is melted with a hot

soldering iron to connect

electronic components on

a circuit board.

Bronze Age sickle

with a wooden handle

and a bronze blade

Iron Age sickle

made of the

metal iron, which

is extracted from

ores (minerals)

ALLOYS

alloys