Metals - Alloys

Humans have crossed through several 'ages' to become what we are today. In the stone age (actually there are three stone ages recognised), 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 realise 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.