Metals - Alloys

Although they have some incredible properties, metals on their own aren't always suitable materials for us to use. Most of the metals we use in our everyday lives are alloys. Pure copper, gold, iron and aluminum are too soft for many jobs so what can we do to improve their properties? Well, we can mix them with other elements to form alloys. Alloys are normally (but not always) a mixture of two or more metallic elements. A good example of this is the mixing of carbon with iron to make a range of steels. Iron from the blast furnace is a brittle material but when mixed with the right amount of carbon it becomes extremely malleable and ductile. It can be hammered and bent into shape or drawn out into thin wires.

Humans have crossed through several 'ages' to become what we are today. In the stone age (actually there are three stone ages recognized), the only metals that were known were those that occured naturally - gold, maybe some copper and some iron from recently fallen meteorites. That made metals very rare and therefore valuable. Copper and tin are easily smelted but soft, however, early humans discovered that they could mix the two together to produce a harder metal that could be sharpened and used for tools and weapons - the Bronze Age had arrived. In Britain, that was about 4,500 years ago so alloys have been used for quite a long time! It took about 1,700 more years for the next alloy to come into use - steel. Humans had entered the Iron Age. They had discovered how to extract iron from iron ore using charcoal and that hammering hot iron that had traces of charcoal on its surface prodiced a material that was harder and more durable than bronze. They had no knowledge of chemistry of course and didn't realize that what they were doing was forcing atoms of carbon into the layers of iron atoms, making it stronger and more malleable.

During the nineteenth and twentieth centuries, driven by the Industrial Revolution, scientists developed many other new alloys which are used for many different jobs. Alloys have usually been invented to be harder, lighter and more corrosion resistant than the metals from which they are made, however there are plenty of exceptions, for example, nitinol 'remembers' its original shape when it is heated and is used to make spectacle frames whilst solder is designed to melt and re-solidify quickly to join other metals together.